Arlington is a beautiful and exciting place to be in the summer. I strongly recommend it for groups of friends or company outings.
The building and grounds are very open, clean, and well-kept. That is certainly not the norm for racetracks, so it is very appreciated. The food prices are quite reasonable depending on where you go, though drinks are slightly expensive. Remember, you can pay to bring in a cooler of food and non-alcoholic beverages. That combined with the low entrance cost and $0.25 minimum bets can make for a cheap day!
Metra is the preferred method of getting to the park if the NW line is near you. Otherwise, parking starts at $5.