Szihn is right about cactus thorns going through the cloth or nylon uppers, but I like a lightweight boot for antelope hunting, so I'm just careful where I put my feet. The weather is usually quite warm, especially in the afternoon, so I prefer something that breathes well. I almost always use either an old pair of jungle boots or an old pair of desert boots. Mine were issued, but I have seen them at surplus stores and I think you can buy them in larger sizes as well. But really, anything that fits well and is comfortable will do for antelope. The conditions aren't terribly extreme, either in terms of terrain or weather (usually), but you might end up doing a lot of walking.
Good socks are important too. I used to be pretty partial to the Thorlo combat boot sock. They had a thick resilient pad underfoot and a thinner, more breathable layer over the instep. They worked pretty well. Now I wear a merino blend sock from either Cabelas or Costco. They are pretty good too. Not as well cushioned, but more breathable than the all synthetic Thorlo was.
Szihn is also right about pads. They are ESSENTIAL. I use pads on both my knees and my elbows. I use the cheap white elastic ones as they go on under my clothes, but the hard plastic ones are probably better.
