It’s really up to you. The process of learning an instrument is so much more enjoyable when you actually want to pick that instrument up every day and play it. If you’re not picky, you should start with the piano. It not only exercises your ears and your fingers, but also creates an extensive music theory foundation. Music theory applies to all instruments, so even if you don’t stick with the piano, what you learn from your Irvine piano lessons will still apply to whatever instrument you end up pursuing.
However, don’t be afraid to learn what your heart desires. Guitar, piano, and violin tend to be the most popular instruments, but instruments like the banjo, ukulele, oboe, and accordion offer just as much depth and complexity.