All the Sceloporus / spiney lizards that I'm aware of can also be sexed by scales and pores regardless of the species. If you flip them over, males have a pair of enlarged scales in the fold just past the vent. Females lack these scales. Mature males will also have well developed pores along the underside of their rear legs. These will be much less developed in females.

Here's a pic of a male S. graciosus:

Here's a pic of a female S. graciosus:

-Alice