I was in the same position that you are in now. What it boils down to is:
a) do you want to save the most money you can
b) find a happy medium with a car that does everything you want
Option a) you are best off selling the truck and buying an economy car. This is the cheapest option because you wont be stuck with the insurance and registration of two vehicles and you will be getting great gas mileage while being much more family friendly. Economy cars have the cheapest insurance and really you can get one with a ton of options right now for cheap. I bought a 2012 Ford Fiesta with 9000 miles on it, full transferable warranty, electrical everything, Bluetooth for calls and audio stream and much more and it was $12,000 from the dealership. It gets 43 mpg and I pay 68 a month for full coverage everything with a $500 deductible. Usually I can not remember the last time that I filled up. There are other options, but I prefer ford and american cars because I do my own work on them and the parts are more available and way cheaper. It still gets out in the mountains, I just have to hike a little further which is a welcome trade for all the money that I am saving.
Option b) If you take on a second car payment and insurance you will not be lowering the cost of ownership at all for years to come. So for this option you are best off selling the truck as well. Then really the only option left to accomplish what you want is a small SUV. Subaru's are nice, but in my experience they get the same gas mileage as a small SUV, but have less space and lower ground clearance. You can find Ford Escapes or similar all over for less than $18,000 and as long as you get one with four wheel drive it will go all over the mountains. Obviously you will have to baby it and there will be limits, but it will take any fire road out there and should get around 25 mpg on the highway. If you do the research some SUV are way cheaper than others to insure, but that all comes down to roll hazard. Just make sure it is not a roll hazard.
Really depending on if you own your truck or not, and the price of gas it is going to be hard to save a lot of money in the short term. You will be paying a little more in insurance, and you will add a car payment that will make up for the gas savings. In the long term once it is paid off you will see the greatest savings with the economy car, but you will be giving up a little utility. The suv or subaru will maintain some utility, but will cost more in insurance and general cost of ownership. Whatever your move is, just plan on not saving a dime until it is paid off.
