From an employer's perspective....

I would not tell them about your back and any accomodations you need until you have meet with them and established mutual interest. There are lots and lots of reason not to hire a candidate. (And by the way... not all companies must comply with the ADA...it depends on the number of employees they have.)

You do not want to frighten them...and bringing up your back will...consciously or unconsciously...cause concern on a number of levels (accomodations, health insurance, absenteeism...) So, if you sell them on your skills and abilities first...they will be more receptive. And you can always turn the job down!

Plus...it is good practice toward getting back into the working world!