Uber and Lyft were taking forever when we were there late summer. We finally gave up after trying two different drivers from SNA and one couldn't find us and one never came. We just grabbed a flat rate cab. So if you are really pressed for time, I would go straight for a waiting cab. With the high prices Uber is able to get these days, the price may not be different at all from a flat rate cab. Traffic will likely be pretty intense at that time of day. I find we need to be on the road by 3pm from SNA to avoid big traffic snags. The cab should use the carpool lane which saves some time (we once had an inexperienced Uber driver who didn't know he could use them and it wasted a lot of time). We LOVE BB so I understand not wanting to miss. Of course, you can try "modifying" the reservation in the app in the hours before your flight, and maybe something later will come up. I often find availability to modify my reservation even when I look at making a new reservation and it says nothing is available.