If I had the choice, I would choose second because they are still kind of at that age where you can still do "corny" things with them, and they are old enough to be independent at times. My second choice would be 4th because I like the social studies and science that generally go with that grade. 3rd would run a close third because I really like that age level. If I were you coming from prek, I think second would definately be my choice.
I have taught all three of your choices. While my personal favorite is 4th, I think you have to decide if you want primary or intermediate. Going from pre-K to second will be a jump, but not as large as going to 4th. In second, the kids are less independent than your other choices, especially at the begininning of the year.You will be doing more guided reading instruction and phonics than in an upper grade. I like 4th because the literature choices in reading are terrific, and the kids possess enough basic reading skills to read and write about books at a higher level than the earlier grades. The curriculum can be challenging, but there is more depth to it. You will need to do more planning in most curriculum areas than for a lower grade because of this concentration of material. I love the personalities of the kids at that age. At second, you have a little less testing pressure and more time to "enjoy" the curriculum than the older grades. Would you be self-contained at 4th, or departmentalized? Our 4th grades switch for leveled math and reading, which is why I chose to go to a K-3 building because I prefer being self-contained. My recommendation would be to observe classrooms at the different levels if you can. If you go into a third grade at this time of year, they are closer to 4th, so you might want to go as low as 1st in your observations to see how a beginning of the year second grader might be. Good luck to you! I don't think you will go wrong with any of your choices.
In the past I taught 4th (one year) and 5th (3 years). This year I moved to a new school and got 2nd grade (it's a pre-k to 2 school). Personally, 2nd is kind of young for me. I'm not really into the "cutesy" activities that go along with this age group. I also find that they require a lot more attention and assistance with things than the older kids. I don't know if it's just my group, or if this is typical of the age, but I have a couple of criers too (which absolutely drives me crazy!!!) Additionally, I like the curriculum at the higher grade levels much better. Really the only plus I see to teaching 2nd grade is that it takes less planning and the grading is much less time-consuming than 4th or 5th (in my state, 4th grade is a big state-testing year). Good luck!