We did the reverse, i.e., Hawaii to Ensenada last April on Infinity. From the time we boarded the bus in Ensenada to the time we arrived at San Diego a/p it took about 2 to 3 hours.
Probably closer to 2 hours except for the following problems:
1. Bus driver didn't speak English
2. Toilets on the bus did not work - and we had to stop at a service station!
3. Clearing customs at the border seemed to take forever. We had to disembark from the bus, walk through customs (just to say hi, I guess!) and back out the other side of the building to reboard the bus.
4. The bus driver didn't seem to be familiar with the traffic patterns at the airport.
Having said that - most of the drive was beautiful as it followed the coast line. We didn't mind it at all and would probably do it again.