My extended family is heavily involved in the Pentecostal\Apostolic (These where at one time one denomination, but it split in the late 50's early 60's if I recall) churches. They took part in founding and running the first ACOP bible college in this province and even in my generation my cousins are on the board there.
Church of God is closely related, and I could learn a lot more about it because a close friend of mine goes to a CoG bible school right now, but I don't personally know the specific differences.
A church is by definition made up of its people, and churches vary widely from church to church even within the same denomination. For example the local Victory church is nigh heretical in many of its pastors views and emphasis, but the one my sister-in-law works at is very well established. Or my Baptist church lays on of hands to heal when there is call for it, while most Baptist churches are ceasationalist and would not.
Pentecostals claim to be the continuation of the Azuza street movement. The Azuza street movement was a powerful outpouring of God's spirit where many fantastic things happened and many where converted. Unfortunately Pentecostal line of thought since the late 70's early 80's has shifted to be quite a bit more cerebral philosophy of conversion. Less prayer and power and more emphasis on why Azuza was successful and how they can emulate the success in terms of number of people converted. In general the movement has weakened a lot since a lot of the scholarly thinking has been about the number of people in the pews. Of course the way the academia think does not always control the church itself, and there is a lot of potential for any given pentecostal church to be full of incredible fire and power, so like I said earlier, its more about the people in the church than the denom.
As a personal observation, the pentecostal and ACOP churches I have seen have tended to have a problem with murmuring about people and to a lesser extent cliquiness. I've seen it in all three that I can speak for, while it may be a co-incidence it is something to watch out for. There are too many people in the church at large that are nice to your face but talk about you behind your back.
In general I have seen reasonably good doctrine, excellent music if you like contemporary Christian, passably good outreach, good churches overall.
I hope you have a good time there. I assume they are not poly positive? Even if not fellowship is good if you can benefit from it. If it is poly positive you can wipe everything I said off the board, as it would be a church beyond denominational boundaries.