As long as you watch for "I'm not interested" signals, don't raise inappropriate topics of conversation (at least, not with a stranger, unless they genuinely come up naturally in conversation), and don't act physically threatening or inappropriately sexual, sure.
That means, don't bother her if she's, eg, reading (other than *maybe* a polite "Hi", but leave her alone if she doesn't put away what she's reading at that point). Don't bother her if she's refusing to make eye contact (other than in the classic shy "glance up, then look down" type pattern). Don't make sexual jokes, or crude come-ons (though a *joking* mild pickup line, eg "Come here often?", is usually OK). Don't loom. Don't sit right next to her if there are other empty seats. Don't touch her without permission. Basically... imagine how you would want, say, a gay guy who was a foot taller and 50 pounds heavier than you, all of it muscle, to act towards you, and try to do basically the same.