Hey OP,

Do you need a folding bike? Also, do you have a local bike store? What's your budget?

I recommend:
1. Go to a local bike store to figure out what size bike works for you.
2. Get a good used. simple bike....a steel hardtail like a Specialized hard rock would be great...as would some hybrid bikes (no shocks, nothing fancy).
3. Or go to a bike coop, and ask to get a throwaway bike...and gradually rebuild it.

The Walmart bikes are generally bad. Ditto for the other one....and I'm a folding bike nut.