From SW New Mexico taking I-8 is a good drive. I-8 (I-10 to I-8 from your area) drops you off right in central SanDiego. There is a 6000 foot climb into the county, but it is easy enough. It is a nice drive. I-8 thru Arizona I always enjoy and seeing the central valley of CA along I-8 is interesting.
And where to stay in SanDiego?? I don't know if you are staying here for a week or for the summer or what, but there are a number of places to park your rig. A couple of the popular spots include Campland By The Bay and Chula Vista RV. They both have internet sites. Campland by the Bay is essentially right at the end of I-8 and is on the bay/ocean. It can be a busy part of town, although very beautiful. There are a lot of RV parks along I-8 from 20-40 miles before it ends at the ocean. These stretch along the area from Lakeside and into Mission Valley which is along I-8 just before SanDiego proper. If you are here to sightsee, these would make you drive a little bit every day to go into 'town' but then again they are a little more remote if this is good for you.
Ask away if you have any particulars,
F350 PSD 4x4 SRW, BanksBrake, FOX res shocks, MagHytec, DP tuner, JohnWood tranny;
'63 hog; ChrisCraft Launch VP8.1 ;
3 hound dogs