Wait, what? Which cafeterias try to block Bitcoin? Also, what do you mean they "block" Bitcoin? There is no central server to prohibit access to. Did you perhaps mean bitcoin.org?

I'd advice you to do everything through Tor. The last thing you want, especially if the cafeteria is bitcoin-unfriendly, is to have some merchant suing you for whatever. With Tor the Internet provider, right as well as the router admin, know absolutely nothing. Without it, it's trivial to notice someone's syncing the Bitcoin network.