Hi zhornbe,
The information, steps, and guidelines in the tutorial post here would be the same no matter how long you had to choose a mattress but your time restrictions would make things more difficult and “intensive” because you wouldn’t have the same time available to test different mattresses to the same degree or make more detailed comparisons between them.
It’s certainly possible to make a choice in two days but I would make some initial phone calls to the options on the Los Angeles list (which is still current yes) to tell them your criteria and budget and find out which ones were most attractive to you and had the types of mattresses on their floor that used the materials or components that you preferred or wanted to test that were in your budget range. I would probably limit your choices to about two or three different stores based on your initial phone calls. If you don’t know the materials you prefer then I would suggest that you focus on stores or manufacturers that had a range of different types of mattresses (latex, memory foam, innerspring etc) so you can compare different types of mattresses and decide which type of mattress you tend to prefer.
It may also be worth considering buying a cheap futon or even a layer of foam to “camp on” for a little while so you have a little more time to choose a mattress that is the best match for you and take off the pressure of having to make a choice so quickly that you don’t have enough time to make the best one or make a “mistake” because of time pressures (which is probably what I would do in your circumstances).
It would be better IMO to sleep a little less comfortably for a few days or a week or two on a “cheap” temporary option than to sleep uncomfortably for a much longer period of time because you ended up with an unsuitable or a low quality/value mattress that cost you much more.
Phoenix