Flight
Flying into Rome or Florence will be your easiest and most affordable options. By car, Florence is about 1 hour and 45 minutes away and Rome is roughly 2.5 hours.
Rental Car
Terre Di Nano, and all of the surrounding hotel accommodations, are located just outside of Montepulciano. The best way to get there is by renting a car, which we recommend you do (maybe pair up with another group!) The drive through Tuscany is beautiful and the ease of getting around before, during, and after the wedding weekend warrants the rental. Several large rental car companies from the US also operate in Italy (Hertz, Avis, Dollar, etc) so we recommend shopping around for the best deal. Autoeurope is one way to search for cars, the link is below. You can also look through your airline for a package deal with your flight. Reminder: rental cars in Europe can be smaller than those in America. Consider the luggage space needed when renting your vehicle!
Train
You can also travel by train from both Rome and Florence for as little as $14 USD (prices depend on the day of the week and time of day). The train will take about 1.5 hours from Florence, and about 2 hours from Rome. The Montepulciano train station is not on a major route, so if you choose to arrive by train, it will involve at least one train transfer on your way there. Also note that the Montepulciano station is a little ways outside of the city center, so you will need to take a taxi or bus to your hotel from there. Uber doesn't exist in Tuscany - only in major cities like Rome!