A spring mattresses is always cooler than a foam mattresses. But the latex mattresses is cooler than anyother foam mattress, especially the memory foam types.
Also the softer mattress is always warmer compared to a firm mattress.
You may just have to turn up your air conditioning.

Well, we don't run our a/c at night, so I'll need another solution.

I know there are latex mattress owners here ... how do others contend with this issue?

What type of sheets are on the mattress? Covers? It could be that you might need to switch to a different kind of blanket/duvet/comforter/sheets in order to sleep cooler.

I've got a latex mattress and haven't really thought it ever slept hot.

Memory foam retains heat. If your latex mattress has a top layer of memory foam or regular foam it will not be as cool as a plain latex mattress.

Also check to see if your mattress pad has any foam in it.

We've never felt hot on our latex mattress. We have a cotton quilted type mattress pad on it. And my DH (a walking furnace) tosses off every cover except the sheet on any bed that he sleeps on. (No matter if it's traditional coil, latex, or air mattress.) He has never complained about our latex mattress feeling warm or hot. But it is only latex. There is no memory or regular foam on it.

Look at the tag that came on the mattress that is attached at the head of the mattress. (The consumer label that is sewn in.) That has to tell you what type(s) of foam or "innards" your mattress contains. Memory-foam is visco-elastic polyurethane foam.

Also, you might want to consider returning it. Some companies have a 90 day trial period. Or call the company where you bought it to ask how come it is making you hot. If all else fails, I'm wondering if using one of those 'allergy' zip covers for the mattress with an organic wool mattress topper might cool things off for you. Wool is supposed to wick away moisture. I have no experience here, so just throwing out ideas until someone with experience comes along. [g]