The cost should be somewhere around $50/month, similar to a cell phone plan. The internet connection speed itself is usually around dial-up speed or a slight step up from there. If you are used to a cable modem at home, you will see a noticeable difference in speed.
The alternative is to just search for an available wireless connection at each home you go to. Chances are, you will find at least one open wireless connection from somebody nearby, although this is not for certain. It is a free alternative, but not 100% guarenteed.
If you can not go for the extra $50/month charge, this would be my suggestion.
One is to purchase a WiFi "hotspot" from your cell phone carrier, OR, you can upgrade your current smart phone (iPhone or Android) to include its own WiFi hotspot. The charge could be around $20-$40/month extra depending on which way you go... But, it will allow you to get up to 5 devices online anywhere you go, as long as you get a good cell connection through 3G or 4G.
At least it looks like the prices for doing this have come down since this question was asked in 2009.
Hope that helps.