to buy or not to buy...in the States; THAT is the question

Hi, I live in europe but am twice a year in the states to see my family. To
use my european provider for phonecalls while visiting in the States is
silly. So I was thinking of buying a pre-paid card in the states for my
telephoning inside the states
while there.
But there is a second question: Currently i have a Motorola Tri-Band cell
phone. I would like to go back to a Nokia, f.i. the 6100 or the 6610 (can't
beat their technique).
I'm really not up to date with the methods of selling and prices in the
states and wonder if i can get in fact a better deal if I get one in the
states.
Can anyone advise me as to what prices would be with a subscription, what
the pro-s / cons are and from which stores? I will be in the Northwest next
week right below Canada.

thank you for your time
jopie