I have an E-PL1, its a nice camera, but I wouldn't recommend it for what you want to do.
1. long zoom.
2. good in low light
3. fast operation
You didn't say what you want to use the pics for ? Publish in National Geographic ? Look at them on a tv ? Make posters ?
If you want the best results possible, a dslr is the answer. But its gonna cost a lot to get a good longe range zoom lens on top of the cost of the body.
Some micro 4/3 camera might be almost as good, but they won't cost less, and their main advantage, smaller size, isn't something you said you care about. The E-PL1 isn't very fast, and even though the body is cheap, a long zoom lens will make the package cost a lot.
Since you're just starting, I think it would be a lot smarter to stick to your original thought, and get either a super-zoom or compact long zoom for $150-300. The main compromise you will be making is low light performance, you will need to shoot at fairly high iso speeds and the small sensors in these cameras aren't as good at high iso as the larger sensor in a M43 or dslr. But some of them are pretty good at high iso if you aren't shooting for big enlargements. With good light they give good results.
And I recommend the compact long zoom, because you can't use a camera unless its with you. The compact long zoom class of cameras are very hotly contested by manufacturers so there's lots of innovation. I have 3 of them myself, the Fuji F505 exr I told you about, a Sony HX5V, and a Panasonic ZS7, mostly because I like all of them so much I hate to part with any of them.