Anyway, if your budget is like ours, you know you have to do more with less. That reminds me of the idea proposed by The President's Commission on Americans Outdoors and the idea that Partnerships are a way to do more with less. (you can pick up a copy of this book on Amazon for US$0.01, see http://www.amazon.com/Americans-outdoors-challenge-Presidents-Commission/dp/093328036X/ref=sr_1_2?ie=UTF8&s=books&qid=1278335142&sr=8-2). It doesn't have to be a Coke sponsorship of your park, after all they don't really need the income (see the impact that Coke has on the World Cup when local vendors are given the boot).
But instead I'd like to (re)propose the idea of Friend's Groups. You know the Friends of (fill in your park). These groups of volunteers can help with the maintenance, upkeep and even the management of your park.
Think your park is too big for this? Well remember the Appalachian Trail is essentially managed by volunteers.