Penn Foster is accredited by DETC (Distance Education Training Council).  While this is 'real' accreditation (as in, its accredited by an accrediting body recognized by the Department of Education), that doesn't guarantee that the next school you transfer to will accept the credits towards another degree. DETC is considered 'national accreditation', and its therefore likely that any other nationally accredited school will accept your credits later (there's a caveat coming up).  However, regionally accredited schools tend to be a little more picky, and sometimes will not accept credits from nationally accredited programs.  Whether that's for good reason, or just to maintain an air of selectivity is not something I can say with certainty, but it is a fact nonetheless. 

Thus, if you have an idea of where you might want to go (later), you may want to give them a call now and ask.  The other factor to consider, is that irrespective of where you earn your Associate's degree and whether you earn an online degree or not, you may not be able to transfer as many credits as you think towards completion of a bachelors, as many bachelors programs can be picky about the associates credits they take.

Good luck! 

 PS -- I'd be interested in hearing back from the folks who moved from Purdue to Penn Foster to get a comparison of the experience.