ItTaxi.com worked very well for me. I made one mistake -- I took a taxi waiting outside the Vatican museums back to my hotel. It cost me €10 more than the ride to the Vatican that morning using ItTaxi. Beware!
Second, health insurance. My Medicare Advantage plan provides excellent international coverage. No need to buy travel health insurance. Check your plan before you waste money!
Third, phones. I have Mint, which uses the Internet, when available, for calls. So far I haven't had to use my international option at all. Also, WhatsApp seems to be preferred for reservations, and it uses the Internet, which I've found available everywhere. Much easier than buying a SIM card and having a different phone number than you gave for all your reservations!
Fourth, consider using a free VPN and get a US ISP. I found some US sites were blocked with an Italian ISP.