The 535 and 535 dual SIM are not really suited for North America. They will only get EDGE speeds on any GSM (SIM enabled) network. The frequencies are wrong for 3G on T-Mo or AT&T.
If budget is the number one factor... Look for a gently used T-Mo 925 or maybe a Blu Win Jr in the brand new category. If that's too much, you'll probably be looking at a 530.