I would not have a trainer that was not certified by one of the national organizations, ACE, AFA, ACSM. In fact, I would prefer someone who had a certification and was an exercise physiologist or a PT. There are a few other smaller organizations that do this, but some are as fly by night as an uncertified trainer...
Many years ago, I did the ACE certification to be a group exercise instructor. It was rigorous and the exam was more difficult for me, with little science background, than my master's comps. I took a very good prep class, as well as self study. The ACE personal trainer exam is the same. I thought about doing it, but never did.
I agree with Helene. Save your money and get certified.