I will add my expierence here. And a suggestion.
First, I suggest a good firewall, Windows XP's internal is ok, but ZONE ALARM (The free version, not the pro) is better in my not so humble opinion.. I get a lot of flack for running Zone alarm behind routers... but that's the way I do it. What don't I get... Well, MS-blaster for one thing, And a whole lot of other nasty stuff as well.
Now: I have used my laptop with my cell phone as a modem (you should use a proper data cable) and it worked fairly well... I don't have Vorizon, so it is slow.. (Vorizon can be slow or fast depending on where you are located, T-moble is slow or slower, though they are improving if the last test is any indication) it works, but grass grows if you know what I mean.
Dial up, when I can get a phone line (on my recent trip that was ONE hour) is faster than T-mobile and may or may not be faster than Vorizion
Wi-Fi, some parks offer it free, some charge, Some you can't really connect, some you can. In addition many truck stops including Flying-J and Pilot offer it, And sometimes a Flying J account works at a Pilot. Flying J accounts cost money, about 20/month more or less depending on the size of the account you purchase.
Finally there is the Ron R solution (Ron's Internet Sattalite) takes a bit of time to set it up if you have the manual job like I do, but I get true DSL speeds from the middle of noplace in particular, So long as I can see the sky, I can type... Was using that connection earlier today, 800+ download (ADSL range) 400+ up,(ADSL can only wish for speeds like that) A very nice connection... Without the rain I'd have broken a meg-a-bit per second