Ya what Dave said...
But to bring it down to a more practical, less theory level. On 2m say you should be able to do better than 60 miles with that radio. I have a good spot up on a hill but I routinely chat with guys on a repeater over 100 miles away with my 5 watt hand held. Some of them are another 50 or 60 beyond that. I have heard people say you can count on about one mile per watt and that may be a good rule of thumb, but it is by no means that max range. In the Denver area I would think there would be a lot of great repeaters that cover huge area of the flatish land to the east from the mountains to the west but I don't know firsthand. While you are traveling in the mountains how well you can hit a repeater is going to depend a great deal on how high you are and where the repeater is compared to you. VHF/UHF (2m/70cm) is more or less line of site for the reasons Dave laid out so you need to have a good shot at the repeaters antenna, but they tend to be is spots that are easy to hit on mountain tops.
So I think you should be able to do better with your setup. Have you checked the SWR on the antenna? Do you have the power set to its highest setting (50w)? Don't leave it there all the time but to reach out you will want everything you have.
To do the long range stuff (DX) you will need a different radio. That's just not what your radio is for. Also when operating HF in the lower bands you need to be a bit versatile because like Dave said there is not one band that will always work. Working HF is very cool but it's kind of its own thing and will take regular participation to keep your skills in good working order. VHF is a great tool for getting communications from wilderness areas that are reasonable close to urban centers. Huge swaths of the west and I would imagine most all of the east fit that description but there are holes and it does have its limits.
There are a lot of smart folks here so ask and you shall receive.
The real voyage of discovery consists not in seeking new landscapes but in having new eyes. - Marcel Proust