Problems connecting wirelessly to wi-fi

We're at a campground that has wi-fi. While my iPhone shows I am connected to wi-fi, my MacBook Pro shows "Wi-Fi has the self-assigned IP address 169.254.158.217 and will not be able to connect to the Internet". I've tried some of the things suggested on searches (remove com.apple.alf.plist for one) but nothing has been successful. Any help, please. Thanks.

I have a MacBook Pro running 10.7.4. and I also can´t connect to any wifi at all even though in System prefs - Network it shows I am connected. In the icon bar the wi-fi has a grey exclamation mark over it. I have had this problem for a long time now, I have to use my (very) old MacBook to connect to the internet! I´ve tried various things but don´t really know what I´m doing. any help would be greatly appreciated. Thanks.