It doesn't matter about the fight stick. If you learn one, it's hard to learn the other. I learned controller first, it took me a really long time to get even decent with a stick. I also know people who learned stick but have trouble using a controller. I've never seen a situation where someone learned a controller and went straight into a stick or vice versa. I say learn Ryu or Ken. Those down, down-foward, forward combinations are the majority of moves. Might as well learn them early.
Edit: Just learn to use the controller. If you bring the game to a friend's house, have people over, or play it somewhere; there probably isn't going to be an arcade stick to use anyways.