I recently traveled from BE to San Francisco.
I'm not sure weather it's the same as over there, but we had free WiFi in our hotel and in about every café, restaurant or tourist location we visited.
Some Belgian providers have certain deals for mobile usage in the US.
At Mobistar, there's a monthly plan with lower prices for texting, calling (in & out) and mobile data usage.
Proximus is enormously expensive abroad, especially when it comes to data usage. They do have a daily plan. For 5€/day you use it, you get a certain amount of texts, minutes and Mb data usage.
Mobile Vikings is one of the cheapest, but I don't know their plans.
I have no idea about deals for Base or other provides.
Unless it's for work, I can't really imagine why you need to have constant network access.
A lot of the people I toured with, used it for Foursquare and Facebook messages. If you really want to do that, keep it for when you arrive back at your hotel.
It depends on personal choice, I guess.
