Best Countertops for Outdoor Kitchens?

What is the best material to use for outdoor countertops in a grilling area?  They're currently covered in Mexican tile that was replaced 5 years ago. The countertop is in the sun all day, and exposed to the elements.  Concrete sounds like the best long-term investment, but I don't want to spend an arm and a leg since we plan to list the house in a year or so. 

The Money Pit Answer

You're right - concrete is an enduring and wise option for outdoor kitchens.  I'm wondering, though, what is wrong with the existing Mexican tile that's only five years old?  If it's not sealed, it might be difficult to clean.  If it is sealed, though, and you want to change it out for aesthetic reasons, I'd recommend against as much, assuming you're selling the house in the next year or two.  
If you do replace the Mexican tile. any natural material like tile granite concrete works.  Quikrete has a DIY concrete kit, and helpful concrete how-to videos, that turn this into a weekend project.