Should I get tickets from US for museums in Florence and if so, which agency?
http://www.uffizi.com/online-ticket-booking-uffizi-gallery.asp you must reserve in advance for academia and the uffizi. pick up your tickets in florence. it saves so much time and is essential really. have fun be safe.
If you have hotel reservations, they may ve able to book in advance for you. very convienient
The first address mentioned is not the official site - this one is: http://www.b-ticket.com/b-ticket/uffizi/default.aspx Hard to say exactly since you didn't leave your dates or mentioned what you want to see. If it is high season and you are talking the Uffizi and Accademia then the answer is probably yes - Maybe you also want to look into the Friends of the Uffizi and/or a private tour - http://www.uffizi-gallery.com/visiting-the-uffizi/friends-of-the-uffizi.html
Yes.
uffizi.com
I highly recommend the Friends of Uffizi membership. Great option for seeing lots of museums in Florence with no lines, no reservations. Check it out!