Go to the gym. The women there will be tired from working out and won't be prepared to immediately reject you. For bonus points, go up to them while they're using a piece of equipment, tell them they're using it wrong, and offer to teach them the right way. They will be grateful, because women love being corrected; and by taking an interest in their workout, they'll see you as a potential mate because you're so into physical fitness, even if you don't look like it.

And don't be discouraged if they're wearing headphones and seem to still be ignoring you. They probably just can't hear you (because of the headphones). In that case, just briskly grab their arm, maybe with a loud "Hey!" so they know you're trying to get their attention. Make sure you let her know it's rude for her to wear headphones when someone is trying to talk to them, she probably wasn't taught that growing up.