The most important thing to consider is this: is the engineering school you want to go to accredited by ABET? Because an environmental engineering degree from an unaccredited school is not worth the paper it's printed on if you want to become a PE. There are ways around this in many states, but the fact is, if it's not accredited, it's not up to snuff. Even if it means a 4-year degree from an accredited school that won't accept your community college credits, it's worth it in the long run. State schools will let you CLEP out of a lot of stuff, which, at $55 an exam (often 3-4 credit hours), is worth considering if your credits don't transfer.
I'm a civil engineer, about to enter grad school to pursue a PhD in environmental engineering. Environmental engineering may be one of the lower paid engineering fields, but environmental issues are gaining increasing attention from government, so the field is probably destined for future growth. And of course, environmental engineers are paid higher than environmental non-engineers.
An internship is good advice and mediocre advice. If you've never worked in an engineering firm before, by all means give it a try. We had an intern last summer who in three months learned a lot about answering phones and a little about drafting and a little about not wearing high heels to construction sites, but really, she wasn't given the opportunity to do much real work.
Environmental engineering is a broad field. You could do hydrology and drainage basin stuff; you could do waste water treatment; you could do environmental impact assessment; you could do environmental remediation. You'd be hard pressed to find a company that will expose you to the full spectrum of environmental engineering, especially not in an internship during what remains of the summer (classes start in 6 weeks).
You're probably better off spending a pre-arranged day at the college you want to attend (and spend the $35 on applying right now, because it's worth it even if you decide not to go). They ought to be able to send you brochures and probably could arrange a tour of their labs and interviews with a few professors who can tell you about their work and maybe you'll understand them. (I did this tour/interview thing yesterday and for the most part I didn't understand them but now I feel really positive about deciphering their jargon in the coming semesters.)
One of the earliest classes you should take is drafting. You can then probably get on part time at a local engineering firm and earn while you learn - it'll also probably pay a lot better than most of the other part time jobs you'll be able to get.
Don't overlook scholarship/loan opportunities. The local university where I live is currently offering a $500 scholarship to over 25s who're going back to school. They don't have an accredited engineering program, but some of their classes transfer to schools that do. Of course there's a limit to the amount of transfer credit, but it's worth keeping in mind.