Can you sue police for slow response time?

Not unless you can prove a gross, intentional negligence. Police agencies are typically immune to lawsuits. Your best bet is probably to make your concern into a political issue by petitioning local representatives, city councilors, etc. to bring attention to slow response times.

However, you should consult an attorney if you feel you have a legal claim, with the full details of your case, as only a qualified attorney - which I am not - can give you completely accurate legal advice.