Frontier Days, aka "Arlington Heights Fest", is always situated around the week of July 4th (a few days prior, and at least 1-2 days after depending on how the holiday falls) and is usually pretty cool.
The fest itself is on the larger side, and is FREE TO GET IN. Contrast that with paying $15 to get into Naperville Ribfest AFTER paying between $10-$20 to park (both of these fests are roughly about the same size and content, too). Parking for this fest can get a bit hectic, but you can ALMOST ALWAYS find some around adjacent side streets, or further down Miner St. by the elementary school. The further down you go, the more parking opens up. You might have to walk a few minutes - just wear comfortable shoes. We have always found parking and it has never been overly far from the fest. There is also a parking garage nearby that one time, we got lucky and found a parking spot in. It's best to just park on one of the side streets and walk to the fest though.
Fest, as mentioned, is large. Tons of carnival rides, food vendors, etc. Usually very crowded, especially peak nights (Friday, Sat, and/or the night of the 4th and big bands). There is no extra charge to see the bands.
This fest has always usually had some cool, bigger bands come thru. Over the years, I have seen BOC, Foghat, Kansas, Little River Band, Eddie Money, and several others. Brett Michaels played last year in 2013. The fest can get very crowded for the concerts especially depending on who is performing. Either arrive early and put down a blanket, or, find a comfortable place to stand having a side-view of the stage. Afterwards, depending on who the band is, you can stand around and some of the band members will come out and sign stuff or take pictures near the back-end of the stage set-up.
Washroom facilities - there seem to be rows and plenty of these, however, I don't recommend them unless it is an absolute emergency if you get my drift, especially women. They are usually dirty, smelly, and dark - this is putting it professionally. Use the washroom before coming to the fest, or if you have to - leave the fest and find a place safer and more sanitary and then come back (it's free to get back in).
Like any fest (especially cheaper or free ones), you WILL see a large chunk of idiot people - usually teens - walking around and loitering because they have nothing better to do. I myself was part of this crowd some years ago. Okay, sometimes they ride the rides, but you get my point.
Fireworks are on the night of July 4th, usually around 9:30 pm-ish.
I usually bring my own water bottle in my back pocket - I think they allow water bottles but various other things you may not be able to bring into the fest unless you hide them well.
I do recommend Arlington Heights Fest. I've gone about 6 times the past 10-11 years or so. Check who is playing at the fest a few weeks before and come on out and check it out, if nothing more - walk around and see the bands from afar - it costs you nothing but gas money to get there.
Would also recommend over going to Naperville Ribfest (unless you are a strict rib connoisseur), which is basically robbery without a gun. read more