The length of your stay in Tijuana will depend on what you want to do. If you only want to have lunch (or dinner) and go shopping, half a day will be enough. I would recommend spending an entire day in Tijuana, though.
In most of the cases it will not be necessary to sleep in Mexico. If you want to party in Tijuana by night, you can go back to sleep in the US.
In case you want to overnight in Mexico, you will find a good offer of accommodation in Tijuana.
♥ Visit Tagulandang Island ♥