My first thought is that "likely worth about 20k-30k less" sounds pretty vague. If it's a $100k house, then that's a big decrease. If it's a $500k house, then the margin of error for determining market value could easily be +/- $25k or more.
You could always ask a real estate agent for a comparative market analysis or price opinion (just tell them straight up that you aren't sure if you want to sell yet, but would like to get an idea of value) and decide what you think based on that. Also, you need to factor in transaction cost of selling if you do sell - you could be out a lot more than $20k.
In the long run it sounds like a bad investment to hold with negative real cashflow, but your current carrying costs are mostly covered by the tenants (except maintenance, potential vacancy, and the cost of you managing it?). I know nothing about the market in Leadville, but if vacancy rates in your area are low, and local demand is high and prices are increasing (like many are right now) it may be worth holding for a while and waiting for things to recover.
As someone who is not a stock market timer, I may be hypocritical for suggesting you consider timing the real estate market. I think I've been pretty good at judging real estate buying/selling opportunities based on market swings, and as long as you can afford to hold a property that is being rented, then it's pretty safe to wait until the market is favorable for you.