Does the 2010 Hyundai Elantra have aux?

Each configuration of the 2010 Hyundai Elantra does indeed have an auxiliary Audio input, but it's more difficult to find and access on some models than others. The upper trim levels that include a double-DIN head unit typically have the aux found on the front the stereo. The smaller single-DIN head unit includes an auxiliary input on the rear of the unit. Even if it's in the rear, You can still access it; You'll just need to do a bit of work to get to it. Once You do, You'll need to find a sufficient adapter cable -- these can typically be found around the $10 price point. Once You have this installed, You shouldn't need to mess with the rear inputs again.