I followed hwy 94 southeast out of San Diego (Southern Tier) ten years ago and even then I would have been more comfortable knowing some Spanish. The hwy went through small rural towns and I was warned to avoid some towns closer to the border with Mexico especially at night when illegals come across. You'll know the bad areas since all the windows and doors have security bars across them.
My last Southern Tier was 2006 and I went north out of San Diego up to Alpine then across to Quartzite. I stayed off the Interstates all the way so there are backroads to avoid I8.
I'm amazed the Southern Tier route maps continue going south along hwy 94 with all the problems down there.
I'm planning on doing the Southern Tier again late January or Early February 2011 and I will work out a new northern route out of San Diego.