If you're talking about Straight Talk, I'd advise you to walk away. There are 3 of us and we all had the $30(?) plan, which is a nice deal. For about a month, none of us had problems. Then we had nothing but trouble and their customer service is TERRIBLE! It took 2 months to get one of the phones replaced and it was a daily 40-minute call of doing the same thing over and over again because they never noted in the account.
When it worked, it was ok.
We switched to T-Mobile and have never had a bit of problem from the service, the phones or anything. As far as I'm concerned, Pre-Pay is the way to go. My 15-year old son has unlimited text and no voice for $15/month (if he uses voice, it's $.10/minute, I think). I had 1500 text or minutes for $30 month and never went over. We recently changed mine and my husband's plans to an emergency use only for $10 (35 minutes that are good for 90 days) because we realized that we weren't really using our phones. So T-Mobile has much more flexible plans without having to buy another phone. (I live in the middle of "nowhere", and T-Mobile and Straight Talk come off the ATT tower, so I lucked out. That's all I get out here!)
Craigslist has lots of prepaid phones too. You don't have to spend as much on the phone as you think.
Good luck!!