AirBnB
These are just a few that I found, but worth looking online and splitting the house between multiple people for a cheaper option. These are much cheaper than hotels I have found
Below are options for Goleta. Goleta is the next town over from Santa Barbara, it is about a 15 to 20 minute drive (you can uber to the wedding.) Could be a good city to check out for cheaper options.
This one is a good option if you are around 6 people to split the cost
RV / Camping
This site is for all campsites in Santa Barbara. Most are already booked for the season, but might be worth checking every now and then as spots might open up.