Here in the Netherlands two cable companies (Ziggo and UPC) are rolling out a scheme so their Internet subscribers - whereever they are -can use the WiFi modems of their other Internet subscribers they happen to be able to receive.

If you're not that lucky your only option is to use free hotspots (a cup of coffee at Starbucks or McDonalds isn't really free, but, well, you get coffee and WiFi for your money), paid hotspots (pay with your creditcard) or WiFi from that lone stupid person who didn't put a password on it.
Or use 3G or 4G from your cell phone provider. But that isn't free and not all tablets have 3G or 4G.

Your choice to buy (and pay for) whatever you need.

Kees