There's boxes and the Jockey Club as well as reserved seats.
Honestly, I believe it's open most of the time for simulcast racing with free admission. Just go check it out ahead of time and see if you want to drop the coin for anything above general admission (free). Here's the seat options.
https://tickets.raceruidoso.com/I'd also suggest doing a quick search for concerts in town. Inn and the horse track both do live music and the last time I was at the Inn, it looked pretty cool. They set up the stage out back overlooking the mountains and lake.
Don't forget fishing as well. The state stocks all 3 lakes (Grindstone, Alto, and Bonito up north) as well as the river with rainbows and other species. You can look up the stocking report each week. If any of them are stocked the week you are there, it would be worth taking some light tackle rods, small J-hooks, fake eggs and worms. We killed them last time and they have license options for less than a year duration.