A good tip for radar is to figure out a safe MVA (Minimum Vectoring Altitude) for any part of your area you aren’t planning to use. If MMMX and KMIA are the two big airports for the day, and you’re at MMMX, you’re obviously gonna figure out the route to get traffic from the northeast down through the mountains to final.
But what about when you get someone putzing in from South America? If you don’t have a whole arrival route in from the south, fly them over anything down there at that safe MVA, and then descend them where you know it’s safe.
There shouldn’t be any part of your airspace where you don’t feel confident flying someone over.