Wrong website! This is a mad dash across hundreds of miles of Italy: ZoomTravel at its worst — and one night in Venice is setting yourself up for major disappointment.

Some information still missing I think, but let's have a stab.

The missing information is whether
   2 days Assisi
   1 week W Umbria
   1 week Rome
is your whole trip; if so, are you proposing to ditch something? Or is this part of say a 5-week jaunt in which most of your time is still unaccounted for? Or do you have a "hole" of a single night between your digs at the Mincio and your digs in Rome?

If it's a 1- or 2-day hole to fill, it seems to me the obvious thing to do is head towards Rome and stay a night halfway: Orvieto is a simple choice, or (less popularly, but every bit as nice) Viterbo.

If you have more than 2 or 3 days, go to Venice by all means, quite different both from Umbria and from Rome: 4 or 5 days in Venice, or a week, will be satisfying (rather than 1 night, which would just be frustrating).

B

No, you can't practically do your trip without a car. The fault lies not with Umbertide, but with your rental unit, which is in the very isolated and tiny hamlet of Racchiusole: no train, no bus, and the barest of roads.

Airport to Umbertide is easy, a series of trains: read all about it.

As far as seeing Umbria, for a first or second time, the Umbertide area is not a good base. (Not good for Tuscany, either.) The main places conveniently nearby are Perugia and Cortona; the N shore of Lake Trasimeno is close by but it's not the lake's best side.

For most of what people think of as Umbria, though — Gubbio, Spello, Trevi, Bevagna, Montefalco, Spoleto, Norcia, the Valnerina, Orvieto, the usual suspects — you'll be spending a lot of time on the road. The area immediately around Umbertide is sparse in things to see, although I won't be proud of you if, having picked this place to stay in, you don't at least see the Badia di Montecorona; and I'll make an exception, in the Trasimeno area, for Corciano.

Away from the board a coupla days and what an efflorescence of opinion!

To simplify things Theresa:

1. Since you're going to have to have a car (and yes, I haven't looked gift horses in the mouth either, and the Mincione looks very nice), you'll have the freedom of going anywhere you want.

2. Throw a dart at Italy, there's something beautiful and/or interesting. Absolutely any place at all, even the most remote, will be the center of a small circle, no more than 25 miles radius, or some other small, reasonable figure, full of enough stuff to keep the visitor entertained for a week or more. (Do see Pauline's Circles if you haven't already done so.)
   Umbertide, like every other place, is at the center of its own circle. Within it, there's hardly any point listing what's available: a map will do. Città di Castello, Montone, Anghiari, Sansepolcro, Gubbio, etc.: all worth seeing. Many other small places even closer, like S. Bartolomeo de' Fossi.

3. Most people, however, seem to insist on seeing The Sights, a sort of canonical list of what Other People Have Seen. Sometimes these places are richer in things to see, or more beautiful; sometimes not. Gubbio, for example, which I'd forgotten (in part because I'm a nondriver and by train it's not a natural trip from Umbertide, in part because I don't like the place), is on the Tourist List, and is definitely worth it. Monterchi is on the List too, and is not: the small village — not much more than a cluster of houses — is dismal, all 20c grey stucco and a very hokey rebuilding of a single medieval tower, with one single painting surrounded by audiovisuals and graphics that no one looks at, for the privilege of looking at which you pay 3E10.

4. With a car, the temptation inevitably occurs to most people to go running off to A Sight; rather as if, having a husband of one's own, one were to stalk Tom Cruise vel sim. (There are of course people who do such things; most of us don't think highly of it, and the waste of energy is similar.) I've done it too, I think every traveler has; but after a while we learn not to.
   Well within the physical ambit of Umbertide, once you have a car, Urbino, Siena, and Orvieto. (I pick this list because they're all at the same distance; 200km round-trip.) Just a bit more driving, and you have Ravenna, Lucca, Ancona and Ascoli; and where will we stop? How much driving do we want to do? Do we really want to spend all our time in a car?
   More to the point, places this far away -- sure, they can be "done" -- have less and less to do with our homebase: and when we've come back from our trip, we'll suddenly realize at some point, that although we were in place X, we really haven't the faintest idea where we were. In sum, the farther afield we go, chasing after sights, the less we will see, first because of the mechanics of getting there, and then because they'll all be out of context. Nothing to hang them on, and ten years from now, we won't even remember them.

To take a personal example. I'm a nondriver, so there've been places very difficult for me to get to, that some kind person — and I do mean kind — has schlepped me to in their car. Almost always such a car trip has had us stopping in accidental places, that had sights convenient to the car (also skipping by more interesting places not on the highway), and my memory of these trips is not as complete as my memory of more organic trips -- even though by now I've got to know one small part of Italy fairly well over the years, so I do have the context to hang these stray places on, and I keep careful notes; but for a first- or second-time visitor to an area, it doesn't work.
   An exception to the rule is if you design a careful trip to a number of places, some can even be quite far away, around a theme: thus the popularity of such things like the Piero della Francesca "trail". If you do your homework, you can design your own around whatever interests you: wine and vineyards, Roman remains, shoe outlets.
   Another exception applies to frequent travellers to one area. Deborah mentioned that, staying at a base near Umbertide, she regularly goes on daytrips to various places — repeating the same places rather often. That's not the same as a one-time visitor: she's built up a solid feel for these places over the years. Another example: almost all my knowledge of Rome has been gained from daytrips. Not one, not five, not twenty, but maybe fifty so far; where a single day trip to Rome in a lifetime would be insanity!

So, having your beautiful accommodations and a car, drive around; doesn't much matter where, the whole area is beautiful. The key is: not too far.

And just in case I come off sounding that ogosh, no I'd never do that....

For many years, captivated by some photos in a book, I'd wanted to see Chioggia, a small town about 15 miles S of Venice. This last trip, I finally did, spending about 36 hours there. By good fortune, I loved it -- it was my big outlier of the whole trip, and you'll notice that since I too was based in Umbertide, it's very similar to your idea of a daytrip to Venice. (The main difference is that there is far less to see in Chioggia than in Venice, and I gave myself two nights there.)

Anyway, while I was in Chioggia, loving it, I bumbled onto the tourist port where a regular schedule of boats takes people to Venice, about an hour away.
   I've never been to Venice.

I stood there for about 5 minutes, maybe I should hop over to Venice.... Sense won out. I didn't go. I still haven't seen Venice. When I see Venice, I'll spend two or three weeks there. All I would have done would be to feel rushed and return frustrated. Again, in an hour (a day, a week) we'll always see the same "amount" of stuff: an hour's (day's, week's) worth; what matters is the quality of the seeing.

But the temptation was there. When it passed, I laughed at myself for it; then went on visiting Chioggia and neighboring Sottomarina: which were one of the high points of my trip.