Hi thatsdopefoo,
There are many combinations of materials, components, and different types of foam that can help a mattress to sleep cooler. Some of the many “variables” that are part of a mattress or bedding that are involved in sleeping cool are in post #2 here.
For those who like the feel of memory foam over other faster response and cooler types of foam … some of the ways that memory foams are being made cooler are in post #6 here.
There are also 3 main cooling mechanisms that different cooling technologies rely on and they are mentioned in the last part of post #4 here. Most of the current advertising is promoting the cooling benefits of various gel materials … either phase change or thermal conductive … but of the three types of cooling methods … I believe that ventilation and microclimate/humidity control which allows the natural cooling processes of the body work more effectively are the most important.
All of this together means that temperature/humidity control and sleeping microclimate are the result of a combination of factors and that by using one or more of these either in the mattress itself or as an add on afterwards (mattress protector, bedding, or various types of mattress pads or toppers) most mattresses types can be made cool enough for most people.
There is a list of some of the better options in and around the Greater Los Angeles area in post #2 here which would also include the closest factory direct manufacturers to the Rancho Cucamonga area.
Phoenix