You could also try other social media sites such as Twitter, Google+, Tumblr, Instagram. The downside is that people don't typically put their addresses on social media sites. It sounds like you don't want to or can't spend much money at this point, but you may need to invest in this process if you're going to successfully serve the defendants. There are services out there that will run a skip trace (or employ other tools) to locate and serve them. It will be money well spent if it allows you to serve the defendants so you can pursue your damages.
Also, if you are unable to locate the defendants after reasonable efforts, you can ask the court to allow you an alternative or substituted service (which is often by publishing the summons in a newspaper in your county). Check the Arizona Rules of Civil Procedure, Rule 4.1 for more details on how to accomplish alternative service. If you end up serving the defendants by publication, you will have to pay to publish the summons, but that does not have to cost tons of money, depending on what publication you use.
Also, remember that you have 120 days to serve the defendants. This time period is calculated from the date you filed your lawsuit with the court. If you are close to that deadline, you should file a motion with the court asking for an extension of time to complete service. You will need to explain the reason for the extension and it helps to outline the steps you have taken to locate the defendants.
Finally, I'm not sure why you don't want to hire an attorney to represent you. If money is an issue, consider the fact that most personal injury attorneys take these cases on a contingency, which means you pay no money up front. You would still be responsible for the costs of the lawsuit (copies, filing fee, service of process fees, etc...), but many law firms will pay these costs and deduct them from your recovery. An law firm will be better equipped to deal with this issue. Ultimately, it's your call. Good luck.
There are a number of internet sites (TLO, Accurint) that provide background information on people, including addresses. Facebook and other social media sites may be helpful too.
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