I've been in this situation. It sucks all the way around. You don't want to lose your partner to long-distance, but at the same time you want to pursue your own dreams. I also did what
@Crayola227 did, and I haven't regretted it. I realized that being somebody's wife (particularly his) was far less important to me than chasing my own dreams, as I didn't want to spend my entire life regretting a decision I made when I was 22. I moved across the country, went to grad school, and now I'm applying to medical school (coincidentally, I met an awesome dude along the way and now we're married).
Ultimately, sit down, and really think about what YOU want--not what he wants, not what his/your family wants, what YOU want. If you don't get in and move to CA to be with him, are you going to spend all of your time wondering "well what if I had gone to medical school?" Are you going to be bitter about it? If you can answer those questions with resoundingly negative answers, then sure, I'd say delay your app, bolster it a bit with grade repair and ECs (because as everyone else has noted, CA med school admissions are a shark tank), and spend some time figuring out what you want--is it med school? Is it dental school? Is it neither? If you love the guy and want to be with him until you're old and wrinkly, then you can move there and figure it out afterwards (provided he has a good job to support both of you in CA...that's also an important factor).
If you're at all unsure of your answers to those last two questions, I'd say don't marry him or at least delay the wedding. It seems harsh and I'm sure that you love him, but it comes down to the problem of having someone in your corner while you slog uphill through med school. Med school isn't a cakewalk from my understanding, and having a supportive partner will help you LOADS. My former partner was super unsupportive of my dream to go to medical school (he even asked me how I was going to manage our household AND be a doctor...because clearly both of those things were entirely my responsibility because I possessed the two X chromosomes
), and I must say, comparing the times I took the MCAT with him as my partner versus my husband as my partner are starkly different. Now-husband understood that I needed to study, never guilted me about having to study even at inconvenient times, and even made dinner for me when I was particularly bogged down in content review. If you want to go to med school, find a guy like that, not some dude who insists that he "can't leave CA" for your career.