Do you mean Cul De Sac Island?
I give you props for doing what your doing.. I mow my neighbors lawn everytime I mow mine because the house is abandoned and I don't want it looking bad.
If this was me and I was in your shoes. I would actually go to all of the homeowners on the cul de sac and try and start a privatized Homeowners Association . That way homeowner dues can be collected in order to manage the island. May or may not work? Or at least get a couple people involved willing to pitch in on the cost
To go completely professional you could have the city install a water meter for the cul de sac ( of course this is spendy though) and then use battery operated valves for your zones. Bringing power in for a controller doesn't usually justify the cost compared to battery op's.
To go your way.. That works too- tap into your main line- install a hose bib ( typically on a post) run a hose from the hose bib to a connection you can connect to into the valves ( It doesn't need to be 2 connections just 1 into the main prior to the pipes.
I would suggest to modify it up some .. If it was me I would extend the Main line as close as possible to the cul de sac. Install a Jumbo irrigation box and setup a
100' 1" garden hose inside the box- then when I want to water I just pull it out and connect it to the cul de sac.. Using a 1" garden hose will help reduce the friction loss and help support the zones at the cul de sac.
Unfortunately there isn't any kind of remote control valve system for battery operated valves. You would have to probably turn them on manually or have it setup to come on automatically after you hook up the hose. You could set up a wire bundle inside the valve box too. Rig it up so when you carry the hose over you carry the wire over and connect to the wires at the valves ( oh god am I really thinking about that orbit jack connector device???) lol!!!!.... then use your controller to run the valves