The food is insipid, It doesn't have enough salt

A close translation to your sentence would be, La comida esta desabrida, le falta un poco de sal' The food is insipid, it's missing a little bit of salt. In spoken english though, I wouldn't use insipid if I was with friends. More commont, The food is not tasty enought, it's lacking a little bit of salt. The food has barely any flavor, it's lacking a little bit of salt.

the food is bland (: