I used to have a HF rig on my boat, I participated in the Maritime Mobile Service Network net, which is a 20 meter band net at 14.300 MHz. Because of the way skip works, from my boat east of Chicago on Lake Michigan, I could frequently hear much of the US east coast down to FL and the northern Caribbean. I had a strong "pipeline" to Texas and in good conditions could hear California and Washington. With 20 meters, you can't hear your own region, although you can generally hear within 10 miles or so. However in bad conditions there was a lot of static and only the strong stations could be heard.
I listened to a number of interesting rescues and disaster related traffic, such as after the earthquake in Haiti, the net was the only way to get information in and out of the country for several days. There were some emotional phone patches as relatives learned of family members who were killed.
The MMSN frequently had check ins from truckers and RVers. Googling "RV amateur net" comes up with the RV Radio Network on 7265 at 8pm each evening, the RV Service Net at 14.307.5 at noon and 5pm. Monday through Friday, and several more which you will have to google for yourself.
20 meters is best during the mid day, and 40 meters is best in the evening.
I have a VHF radio but have not used it much, where I live in a rural area there is almost no traffic, even on the repeater.
Unfortunately HF rigs tend to be expensive, a new low cost radio is $700 or more. A good used one is a Kenwood TS-130S,
http://www.ebay.com/sch/i.html?_nkw=kenwood+ts-130s, usually available for under $500. The Icom 706 is a great radio but expensive. Maybe the Chinese are making HF radios now, that would be a breakthrough to get a decent HF rig for $300 or so.
The real key is going to be setting up a good antenna with antenna tuner. I wish I had a good recommendation but I am still trying to figure out a low cost option to install in the van.