[Jess~]

about faking the GPS, i've actually been planning things myself.

if you have a car, park where you're "supposed to be" and leave your phone in there, then either walk to where you really want to meet your friends or have one of your friends pick you up.
or if you don't have a car, go to some place where you can rent lockers (can't think of one off the top of my head... maybe an ice skating rink or something?) and put your phone there. just tell your mom you're going there and then do the same thing after she drops you off - walk to where you really want to be, ride a bus/taxi, or get picked up.
OR you could set up a plan with a girl friend, that your mom approves of you hanging out with, where you could drive to/be dropped off at that friends house and leave your phone THERE, then go to the other place. just make sure it's a really chill friend who wouldn't rat you out, and make sure you leave a good lock on your phone and shut it down when you leave it at their house. (you never know, with friends.)

just make sure that you wear a watch or something so that you can get back to where you're "supposed" to be in time to either drive back home or be picked up by your mom.
it would be awful if you lost track of time and your mom went to pick you up, only to find out you weren't there.

EDIT: or, y'know, you could follow everyone else's advice and be honest and open and all that. yeah, that would probably be better... i guess. ugh, sorry, i got excited there. -.-
but just in case the sneaky, lying path is the one you want to take, i'm here to help you devise a plan whenever you need me. c: