As a local, I second that don’t ever go to Mexico (Tijuana). It’s very dangerous. You can still go near the border and see Mexico from the US side (LOL). While there, you can go shopping at the Las Americas Premium Outlet. The border is only about 20 miles from Mission Hills.
Side trip recommendation: You can go to Palm Springs and go ride the Aerial Tramway. Great view from atop the mountain. You can also go to Joshua Tree National Monument while there. But this is like a whole day affair.