I definitely think so. At least bi. But we are forgetting, she's a character, not a real girl. So she is whatever Dan makes her out to be, so here's my theory:
Dan, in his consistent attempts to entertain both young and older audiences with a few adult jokes and themes, probably does set Sam up as a lesbian/bi. He will make a few "barely-there" references to it every now and then, but of course will never say it outright. He will just keep putting in inuendoes and tiny things that hint at it, leaving it almost entirely up to the viewer's imagination.
By the way, here's another thing I thought of a while back, in reference to this. In iDate a Bad Boy, when Sam is having nightmares about a monster stealing her soup, here's the meaning of the dreams:
If you pay attention, she only has the dream right after or shortly after Carly goes off with Griffin (twice).
The monster = Griffin (representing any and all boys; it has nothing to do with him personally)
Her soup = Carly (something she wants, being taken by the monster.)
Makes sense, right?