It would be smarter tactically to start in a smaller venue, with much weaker popular support for illegal immigration, fewer immigrant-dependent politicians, less than a 50% lawyer to citizen ratio, no whiny celebrities/newshounds, and a judiciary that considers the US Constitution as more than a suggestion. LA would be a tar pit that would suck up far too much political energy. Achieve legal precedents and successful implementation where opposition is weakest, before getting into a death struggle with the big dogs.
All of which is a valid point, except for the fact that LA is, in fact, already weak. The city is already millions in the hole and a fight with the feds (especially after the aid is cut off and they have to sue to get it back) could be just the thing to wipe them out.