im not totally sure when this goes into action but i know your going to need a passport soon to cross back into the states from mexico even on foot. iv heard as soon as jan 31st.
idk about that area specifically but i know in tj the cops are pretty corrupt. just keep to yourself and dont draw much attention and ull be fine. as far as driving your car over i have friends here who drive their cars/bikes over and dont rly have problems, again, its about not drawing attention to yourself