Hi Chicagoshannon
We are a homeschooling family in IL, Arlington Heights, to be more specific. There are many homeschooling groups around this area. CHAMPS, HELP, HEART. I know Champs in now on the computer and they meet in Mount Prospect. Also, many libraries also have information on how to get in touch with home schooling groups.
As far as graduating goes, my oldest child just graduated from HS and he had the option of attending a graduation ceremony at our church. Caps, gowns and speeches, but he didn't feel the need to go, so we just had a party for him instead.
As far as homeschooling in IL goes, you don't have to report to anyone. It is really up to the parent to be diligent and cover all the appropriate subjects. My high schoolers, once they have turned 16, started taking an occasional class at the local community college, to prove to themselves and the colleges that they were interested in, that they were capable, and did truly deserve the grades I gave them.
We have also been involved in a group called Christian Youth Theater, and that gave my children many opportunities for socialization. They were involved in acting, singing, and dancing classes, and were involved in 3 musicals each year. Their best friends were usually kids in this group. It is a very full and busy life. Many of the families in our CYT group homeschool so it is also a good way to make connections.
I have not used the Horizons curriculum, but in the younger grades, I used a combination of Sonlight and Abeka.
Best of Luck in making your decision.
We went to MNSSHP in 2006 when we took our oldest boys for their first trip, we loved it, but we haven't planned for it this time. Since my mom is going with us, we're enlisting her help for one night of babysitting and DH and signed up for the Expedition Everest Challenge though. I'm excited about that, but nervous! I've got to get crackin' on a couch-to-5K program next week. 
