Unfortunately, the hospital cannot turn you away for not having insurance, and they do not advise you as to whether or not your insurance is current. (This is to encourage people to be seen for life threatening emergencies, and hospitals can be charged with negligence if they are turning patients away with these conditions).
However, to deal with your medical bills:
The form that the hospital should be sending you is called a "Payment Assistance Application" (the billing department has this, send them a written letter asking for one (keep a copy)).
When you receive this, complete it promptly, submit all necessary copies or additional information, and send it back (keep a copy).
The welfare that they are going to assist you with is getting Medical/Medicaid for you dated retroactively to the date of service. This is why you want them to assist you with this.
If they do not assist you (they should), or if you appear to be getting nowhere with their assistance, visit your local county benefits (welfare) office and ask for assistance signing up for mediCal. Make sure to tell them that you have outstanding medical bills (give them the date and details) so that they can sign you up for retroactive benefits.