The snowpack is deeper than normal this year at treeline/alpine and below normal below treeline. You should check the BC government snowpack data online: [url]http://www.env.gov.bc.ca/rfc/data/asp/realtime/basin_scoast_lfraser.htm
Choose the Upper Squamish station to see what snowpack is like around treeline at Garibaldi - this will show you if you'll be postholing, skiing, etc.
The bergschrund on the Warren Glacier side is the crux of that route but can usually be crossed throughout the summer with increasing difficulty.
If you want to come in from Elfin Lks side (much longer) and climb the East Face the broken glacier below the face is navigable in the summer and may be easier than crossing the Warren bergschrund.
June should be fine for some kind of ascent.[/url]