All the Sceloporus I have dealt with can be sexed at any age by looking for paired enlarged scales just past the vent.

Here's a male

Here's a female

Mature males will also have enlarged pores on the underside of the thigh and most will also exhibit differences in coloration. These characteristics will only be visible in adults while the pair of scales will be present at birth / hatching.

Good luck with your guy!
-Alice