Well, I definitely enjoy both sex and fucking, but I do both with the same person on a regular basis... so that's kind of a different situation.
And hey, I would say that both my husband and I "appear" to be sexually conservative in public, but we raise hell in bed (and other rooms and settings). So, you never know...
But I'd say, if you are DEFINITELY looking for booty-call status only, then make that clear from the get-go. Don't lead her into thinking you want to have "sex" or even a data or relationship, when you just want to "fuck," period. Then, even if she ends up not liking you, at least you were in the clear by being honest about your wishes. And who knows, she just might be up for a fuck!