UCSD has a centrally managed wireless network that covers the entire campus. This network is managed by ACT. The first place you should look to find information about wireless networking is here:
The main thing that you have to be aware of is that you will most likely want to be connected to the UCSD protected network. This will require you to enter your campus active directory password to connect.
You, and your guests, may connect to the UCSD guest network. The UCSD guest network does not require a password. However, there are a number of limitations on what you can do with it. Please note that traffic on the UCSD guest network is not encrypted.
If you have guests from a different university, they may be able to connect to the campus eduroam network using their password from their home institution. Connecting to the eduroam network will give guests similar functionality as the UCSD protected network provides.
If you have difficulty connecting to the wireless network, you can contact CSEHelp for basic setup assistance. For more intricate problems, you should contact ACT directly.