Springtime will be great, and of course a couple of days is good! If you need help with accommodations here in Carlsbad or Oceanside, I can help, although other places in the SD area are a mystery to me. I can still try to help, though. Again, springtime is good, and you probably won't have much trouble finding places to stay along the way, except maybe Vegas; it's a very popular time to be there because it hasn't gotten *hot* yet. It might be to you Brits, though 
If you plan on driving through Colorado, you should hit Ben (SOW) up for a pint. He's fun
Yeah- we get some really good bands at Del Mar. You only have to pay the $6 admission ($3 if you sign up for the membership, which is free- although, you might have to be a local; I can't remember), into the races before they end for the day, and you get to see really good music at a great outdoor venue looking at the ocean. The races are fun too, but that's moot if you won't be here in July/August. Sorry. There are plenty of other fun things to do, anyway. We should do one of your days at the beach, but I'm gonna make you both wear SFP 128

If you plan on driving through Colorado, you should hit Ben (SOW) up for a pint. He's fun

Yeah- we get some really good bands at Del Mar. You only have to pay the $6 admission ($3 if you sign up for the membership, which is free- although, you might have to be a local; I can't remember), into the races before they end for the day, and you get to see really good music at a great outdoor venue looking at the ocean. The races are fun too, but that's moot if you won't be here in July/August. Sorry. There are plenty of other fun things to do, anyway. We should do one of your days at the beach, but I'm gonna make you both wear SFP 128

Nolite te bastardes carborundorum.