How long will homemade Pico de Gallo last in the refrigerator?
The Pico de Gallo I make (plum tomatoes, white onion, fresh jalapeno peppers, lime juice, a tiny bit of olive oil and chopped fresh cilantro, salt and pepper) will last approximately 1 week if kept in a sealed container in the refrigerator.  Over that time the tomatoes will get a little mushy and the cilantro will wilt.

Perhaps you can have everything else mixed and just add the chopped tomatos and freshly chopped cilantro when you are ready to serve?