Yes, as for entrance fee, it doesn't make a difference if it is 0 or 28. So put that up. For restaurants, you can easily go up to 13.50. Like Taun says, don't overbuild. If you start a zoo, with say, 20.000, a small exhibit soon costs up to 10.000, then you still have to build roads and guest accomodations.
There are ways to get more money. One of them is getting a prize for great exhibit design. The first one is 0, the second one is 15.000. Take an animal which has an easy exhibit, like a thompson gazelle. Then build one for the zebra. You will have another 15.000 for a third exhibit.
You can also use quick breeders, sell off the young, like warthogs.
All starts are difficult, though. More so when you start with few money. I notice from when I have about 10 exhibits, it starts going easier. (I can build, without having to wait for too long between building periods.) Restaurants, giftshops, etc.. are important to make money. Don't forget to build them.
Also if you have a show, build a restaurant next to it. People are very hungry when they leave the show, guests tend to get displeased if they don't have food/drink/bathroom right away. Plus, you make extra money.