Can I get a divorce if I have no clue where my ex is last known address was ours, he was an illegal immigrant?

Legal or not makes no difference. You file for divorce and if you don't know where he is, you publish against him. Contact an attorney to help you.

Yes, you can still get divorced. The power of the Court will be limited - e.g., the judge will not be able to deal with property or financial issues such as maintenance (alimony). But when the process is complete, you will be divorced. I would suggest you contact an experienced family law attorney to represent you - this should not be a complex matter, but an attorney will make the process much more efficient for your.

The advice of the other two attorneys is accurate. You CAN file a Petition for Dissolution, and, if you are unable to determine his whereabouts (do an internet search to show the Judge you tried), you may obtain Service by Publication. If you do it right, you will be "divorced". However, you need jurisdiction over him (to have him served) to determine property distribution, allocate debt, and deal with any issues related to a child you may have with him. An immigration attorney can help answer any questions about the ramifications on his status. Good luck, and get free!