Upvote:3
If you are trying to extend your time in the US by traveling to Mexico, that is unlikely to work unless you apply for a B-2 visa while you are in Mexico.
If you want to go to Mexico for 48 hours while still intending to leave the US before your I-94 expires on 29 April, there should be no problem.
You should probably check your I-94 to be certain of your departure date. April 29th will be your 91st day of presence in the US after arriving on January 29th, and the US appears to be counting the 90-day period inclusively in recent years. It's possible that they've been applying that policy inconsistently, however.