I have lived and fished in Squamish for 20+ years now and the summer months are not the time of year to fish the rivers. This system is very much different from the valley streams in that there are no lakes to bufer the flow so stream flow is dependant on glacial melt and rain events. The Squamish river is very glacial at this time of year with visablity being under 6 inches. The tributary streams are better but most of these streams ( the Mamquam and Cheakamus) have tributary streams that colour the river downstream from where they enter those streams.
As far as fish species this time of year, there are chinook adults, char and some trout. Forget about any significant trout populations in the Cheakamus as they were killed in the chemical spill last year or are protected by a angler closure in the upper river near Daisy Lake dam. The Cheakamus is currently high and marginally fishable. The Mamquam has nice colour but is on the high side. Don't waste your time on the Squamish as it's glacial grey.
Just a reminder that all chinook adults are closed to retention but you may keep chinook jacks under 55 cm. There is a year round bait ban.
The last info is that the chinook are predominetly white fleshed fish with about 10% of the population being red fleshed. On the plus side, the whites here do not stink like the Harrison / Chilliwack white chinooks in the valley.