Not all personal trainers are bad. Thats why you don't sign a contract, just pay for a couple days worth of sessions to see if you like the trainer. Trainers are good for people that have no idea about exercise or need that extra pep to keep them motivated.
I warn you to check their credentials. There are trainers out there that are training with expired certificates or don't have a certificate at all.
I read that you can get a PT certificate online over the weekend.
Make sure the certificate is ACSM, ACE, or NASM certified. There are others that are good, but I am currently studying for the ACSM PT and HFI certificates.