Tips for StarPixie, a young performer who got harrassed over Halloween weekend by some teen boys who wanted to mess with the little girl mime. Oddly, in all her performances bellydancing, she never had a problem. She puts on gloves and makeup, boom, she's got trouble.
there are a bunch of things you can do to "make yourself bigger." (excuse my lack of caps; i was injured and type one-handed for awhile now)
first off, scot is right: the more you think of yourself as small and vulnerable, the more you will be.
second, never underestimate the power of a dirty look.
find your "safe" spots before getting really into a gig, so you know right off where to go, ie, the security station, the large friendly guy working the dunking booth, a police officer, another, larger, performer, the women's bathroom, etc.
go easy on the coy come hither stuff with those who are saturated by hormones or alcohol, or, god forbid, both. instead, square your shoulders, chest out, chin up, and meet their gaze straight on with a "no bullshit" message in your eyes. full professionalism.
build up your "personal bubble" to about two to two and a half feet. carry this with you at all times. it's fine to invite people in closer if you want to, but that's at your discretion, not theirs.
i have used my knees, applied with some force, as a method of self-defense. not often, and i'm not proud of having allowed the situation to deteriorate far enough that physicality became necessary, but it was effective.
refuse to play the game. let them have the hat, or the prop, or pick you up, whatever, because an angry struggling mime is amusing to bullies. a limp, annoyed one is just a burden. you will gain knowlege of when to use this tactic as you gain street experience. i once had a patron pick me up and carry me away at the ren fest. i just waited until he got tired of carrying me and put me down. then i gave him a dirty look, brushed myself off, and went about my business. i have lost a couple of props this way, but proportionately, very few, and never my favorite ones. standing patiently, unmoving, hand out, will often force the return of an item, also.
i hope this is helpful. good luck, sweetie!