Can I leave the US if I have filed I-134?

I am assuming that you are planning to leave for a short period of time, not depart the US permanently.  The USCIS form I134 is a legal contract between you and the United States Government.  Therefore, traveling overseas or even spending a lot of time in the US is not an issue, but after you submit the form as an affidavit of support and the immigrant needs help from the Government that you should have provided, Uncle Sam will do everything in its power to find you and make sure you pay.