to AllDeaf Lil_Country_Gal, I hope you will enjoy your stay on this forum. You will make a lot new friends, friends who will/are more understanding.
Those friends you mentioned, are not your friends at all, when they cannot accept you for who you are , or how you communicate. If it is within reason, you need to let them know that you come from a unique culture. As for your ASL, they need to understand through you that this is the way you communicate, through sign language, like they communicate orally.
If they are still ignorant towards who you are, then just ignore them, because "what goes around, comes around", then they will wish they hadn't mimmicked you or made fun of you, because in time, they may need your help.
Just hang in there, find friends who are more understanding and more accepting. I wish you the best of luck, and maybe you can ask them if they would like to learn to sign, I bet they will find it pretty neat.