hello board..
american citizen living in san diego here.

if i cross the border on foot from say ysidro into mexico, and plan on heading south all the way to mexico city for a 4 week excursion, will i have to get a tourist card?

will i be able to just go straight to the tijuana airport and get a tourist card there or MUST that card be picked up at the border?

also, when crossing the border, mexican border patrol dont really check anybody for documents do they? in other words, the u.s wont have any record of my exit?

thanks in advance.