I worked at the Safari Park. It is a competitive field and you'll definitely have to work weekends and holidays. The jobs though are fun, and the atmosphere and the care of the animals is phenomenal. It definitely is one of the best zoos to work for, just don't expect a full-time job. I was there for over 3 years and worked into different positions but never made it to full-time before I left.
Getting time off is competitive, too. If you're at the bottom of the chain, you have to wait until everyone else fills out the leave calendar, and you most likely will not get all the days you want... and you'll have to know in advance when you want off. It is difficult to get weekends and holidays off.
The hourly pay is actually great for tour guides, keepers, handlers, exhibit attendants and trainers, but again, not full-time for most, so it breaks even.
You do get discounts and free tickets to the Zoo and Safari Park, and they used to do SeaWorld too, not sure if they still do.
The animals are definitely the best part of your day. You are there to make a difference, so it is rewarding. Just not financially.