Generally if you fly from Tijuana, you would save like $80 in international taxes. However, it looks like LAX-Los Cabos starts at $198 RT and LAX-La Paz is $188, while Tijuana-La Paz is $260, so you would save on tax but pay more in airfare.

If you have easy access to travel agencies in Tijuana, though, you might find a good deal on an air and hotel package-- my experience, based on living in Mexico for 1 1/2 years, is that domestic packages sold by Mexican companies (AeroCalifornia, AeroMexico Vacations) have better deals than international ones (Alaska, America West Vacations et.al.). It may be worth a day trip to Tijuana to check it out. Of note, though, is that there isn't through service from Tijuana to Los Cabos, so you'd be hard pressed to find a package.