Luanne said:
I just did a mapquest check and it looks like the drive from Las Vegas to Escondido is only 4 1/2 hours. Personally, there isn't anyplace I'd be tempted to stop. As I recall, there isn't much in Barstow.
Well, harumph, Luanne. We residents of the Temecula Valley are incensed

!! We live in a nice place here!! [Residents of Barstow are on their own here. Although there is a ghost town -- Calico -- nearby.]
First of all, the time it will take depends on when you are doing this drive. If it is anytime Sunday after 10am, it will definitely take six hours or more via I-15 as half of LA returns from Vegas. At other times, it might be as little as 4.5, but could still be six.
You can detour through Joshua Tree and stay in Palm Springs or another desert community overnight if you like, continuing down route 371 (I think) and then 79S through Temecula. Stop at a winery or two or three. Many are open weekdays, and about 15 on weekends. If you have any money left, the Pechanga casino is the largest and some say nicest in southern California. My neighbor John Cummings will likely expand on casino possibilities.
If you'd rather, you can stay on I-15. There's a factory outlet at Barstow and huge mall at Ontario if you like that sort of thing. Coming down past Corona, you can check out the Glen Ivy spa, or the nearby Glen Eden sun club, where you maximize your sun exposure by ... oh, you get the idea. Stop at Tom's Farm in Temescal Canyon for a snack and fresh produce. Google will direct you to information on any of these.
If you want to see Murrieta's old town, we'll be happy to show you our grain elevator ... or visit the Santa Rosa Nature Reserve. Temecula's old town has been restored and is full of shops in the style of the late 19th century. And you can get to the wineries and Pechanga from this direction too. There are a few nice B&B's, but now you're about fifteen miles north of the Welk resort. Hope to see you in April!