There are a lot of maps that have multiple spawn points.

When we are creating maps, is there anyway to designate which spawn points creeps come out of? Or, what the order of spawn points are?

I really wish there was, but as far as I know, the creep spawns from top down and from left to right.

As of now, no. I believe mahleumon has it correct. Although that doesn't mean I can't add this feature one day. Let me get multiplayer btgtd done, and then we can look at new features :)

To be total correct, they begin to spawn in the uppest left entrance, then go from left to right. When there is no spawnpoint left they spawn in the next row from left to right and so on. That means if an entrance in a lower row is more left than an entrance in an upper row, the will spawn in the upper row at first.
If you are in the editor they will spawn in the order you place the spawnpoints.