I defaulted on a 10k car loan which my dad was co signer on. After about 3 months of not paying, One morning I woke up and the car was gone... (I had to go track it down to get my plates and things from it too!) Anyways this was almost 4 years ago now and they have never come after me or Him for it..
I also have two defaulted (and maxed out) credit cards. and have had various other "minor" credits I have been given on things like laptops, cameras etc...
Like Matt said unless someone can prove you intended to default from the start, there is very little that can happen from a legal standpoint.
They can only affect your credit and Here in Canada the stature of limitations is 7 years. However not everything is so simple as it does take some sacrifices. For example lets say a debt collector call you and you answer the phone "hello" and the collector asks for you by name and you say "speaking" right then and there your stature of limitations just started all over again!
The best and hardest way to pull this stuff off is make your self invisible so to speak of every system. which means banks, government, registered clubs, library etc..
Currently how I do it is to make "them" chase me all over the Country. I have various mail address, phone numbers(I screen every call anyhow and my cell is prepaid under a alias), emails etc... and the less you tell others your current situation(s)/location(s) the better.
I can't truly offer any advice/tips on dealing with the loan where your mother is involved as that is something only you can decide how to act on. They may or may not come after her...
But something I do suggest you do is utilize this wonderful thing called Internet to research credit, credit scores, and US federal law surrounding such. As the more you educate yourself the more you can make sound decisions that's right for you.
and as a matter of interest have a look this web site
http://www.natural-person.ca
and also I recommend reading about George Gorden
http://www.georgegordon.org
Whatever you do, good luck!