[VivaLaViking]

I would count the A, it's the 2 that would concern me because you are putting yourself in a position to hold the sucker straight and likely in a reverse impled odds position (2 - 5 on board). But to answer your question, you have 9 outs for the flush, 3 outs for the A and 4 outs for the 2. 16 outs, that's 57% probability after the flop. So if you would feel comfortable with those outcomes it would not be an error to call up half the pot after the flop. It does sound like you are referring to a limit game. So you should probably call (or raise) to the river.