Xenia L.
Yelp
This isn't the fanciest hotel you'll ever stay, but I challenge you to get anything nicer for the money in Oceanside.
On a spur-of-the-moment trip to Oceanside, we were looking at paying $180+ for a room at the Holiday Inn, which is nice, but hardly worth the money. Instead, we wound up with a full suite here for less than $100. Our room had a full-size fridge and stove, the bed was comfy, and the shower was nice. None of it was fancy, but it's way more than we would have gotten anywhere else. We were in stumbling distance of downtown and the beach, and the manager was the single nicest person I've ever found working at a hotel. Seriously, it's worth going just to meet a human being that friendly here in SoCal. There was a cute cat, too.
Downsides: You're right by the train tracks, so if you plan to sleep late or are sensitive to noise, this isn't the place for you. There's no online booking. The water pressure isn't impressive. If those things don't bother you, you're going to have a great time here.