I just tested my water and I have an ammonia reading of about 2, nitrite about 2, nitrate about 5 and PH almost 8 =/ I did about a 25% water change. The tank has been running for almost 4 weeks. Did I do the right thing and is there anything I can do to speed up the process? How long should it take for a 5.5 gallon tank to get established? Also, will the PH naturally come down as the other readings improve?

yes, once your tank cycles your ph and everything should balance out for the most part, but unfortunatly i've found that most aquariums under 10 gallons just dont cycle at all.. tell me, does your tank have a filter? what kind and how many fish do you have? on an unfiltered tank that small I personally would recommend almost a 50% water change every other day to keep the ammonia down.. there are items such as ammonia eliminators and bacteria boosters you can add but in my experience they just make the water more unstable and harder to maintain in the long run.

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10g- 2 hi-fin fm platys, 3 koi & red wag sword fry
40g Breeder- 6 danios, 4 female swords, 1 male swords
"I was born with nothin and I still got most of it left."- Seasick Steve

You did the right thing with the water change. Ph should not go down, but 8 is good as jca said.

My filter is a top fin power filter (one that hangs over the side and you change the cartridge every 3-4 weeks). It's just a cheapy one that came with the tank...I was thinking about getting a new filter...something like this:
Marineland Penguin Power Filter Up to 20-Gallon, 100 GPH. It has a little bio wheel and is supposed to get rid of nitrite/ammonia better and retain the good bacertia better. Does this sound like a good idea?

Up until yesterday I had an African Dwarf frog and a Mystery snail in the tank (as well as an elodea plant). Yesterday I traded in the snail after finding out they foul up the water quite a bit and got a nerite snail instead. I also got another live plant.

Any more thoughts/recommendations? Thanks everyone!

From what I have learned, don't change the filter pads just take it out rinse it in some old tank water (not tap water) to de-gunk it and then reuse it. If you change the filter cartridge it takes away any good bacteria you have established and you end up in another cycle.

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"Being ignorant is not so much a Shame, as being unwilling to learn".-- Benjamin Franklin

the filter you want will definetly do the job but honestly i wouldnt spend the money, at the moment i have a ten gallon with a few glofish, a swordtail and a gold incan snail and its holding up quite nicely and i run it with an aqueon quietflow 10 power filter, think i paid no more than 20 bucks for it, the marineland is more expensive but it might hold up, better in the long run? its your choice

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10g- 2 hi-fin fm platys, 3 koi & red wag sword fry
40g Breeder- 6 danios, 4 female swords, 1 male swords
"I was born with nothin and I still got most of it left."- Seasick Steve

I read somewhere its not good to rinse and reuse filters because of the carbon in them? I think the thought was it breaks down and gets into the water. Anyone know anything about that?

Just rinse out your pads and don't worry about carbon. That function is obviated by the simple act of the water change. In a small tank 50% at least once a week is the way to go. I wouldn't bother with that new power filter either, just change water and invest in Aquasafe instead!