Grinding etiquette???

I was at a fraternity party just dancing havin fun, drinkin. of course, guys are gonna come up to u and grind. and its true, i do want to grind on a guys crotch, but I hate it when a guy just comes up to u and starts rubbing on u. I would like him to at least say "may I dance with u" or something. Is this too much to ask for drunk college boys??