Does anybody in your group speak Italian? That will help some.
It has been a few decades since I was in Italy. However, my experience was that English was fine in the big tourist cities (Rome, Pisa, Venice, Florence, Milan, Bologna, etc). However, if you get out into the smaller cities, you will have to improvise a bit.
Now, some of that could have changed recently.
Now, there are very good trains and buses in Italy. So, you could plan a trip so that your companions would take a public train or bus to the destination, say within 50 miles, and you would ride your bike there.
I'm not quite sure why you picked Umbria. There is Perugia, and the University for Strangers... (Oh, Stranieri, or Foreigners).
A little side trip to Assisi would be fun. Learn about San Francesco.
I accidentally bumped into some odd Roman ruins on a hillside just north of Terni (by bicycle). There was an old Roman road with the deepest ruts I've ever seen worn into solid granite.
Lago Trasimeno was interesting. I'm sure I swam in it but I'm trying to remember whether the water looked clean.
In Tuscany, one can certainly spend a couple of days in Florence.
I don't really remember spending much in the areas surrounding Florence.
I spent a lot of time in and around Parma. The PO valley is very flat, so you can really make tracks by bicycle. However, at the time there weren't many people that I encountered that spoke English there. I think I went to every castle within about 50 miles of Parma, of which there were quite a few, each one unique.
Perhaps the most famous was Canossa, but also one of the least preserved ones.
None of my traveling was with a tour group. Some places would have organized tours. Others would essentially give a private tour.
If you are interesting in Italian or Renaissance art, then it would be worthwhile to do a little research before you go.