Whats the best time of year? See above
Whats the vis like? One October day I hovered over the bow of the wreck and was able to see the bottom clear as a bell as well as the bottom going away. Wish I had my camera for that one. That day the viz was easily 100 feet plus. During the summer months you can expect 20 - 40 foot. Remember after every rain MMSD dumps raw sewage. I tend to avoid Milwaukee at these times. I find it sad that they blame the Seagulls.
Water temp? Surface temps March through May run from the mid 30's to the mid 50's. Same for October through November. Summer months, the surface is generally warmer, 50 to 65. Bottom temps vary from mid 30's to mid 40's. There are fluke days, like after theres been a few days of east winds in summer, that the bottom that deep can push 60. I wouldn't bet on it though. Expect cold.
Cold, we were the in July Temp at 73' was 44*
Wetsuit or drysuit? In summer time I'm fine in my farmer john style 7MM with 5mm hood, gloves and boots. Were assuming two single tank dives with surface interval of course. Most of the time I go dry suit with dry gloves.
We wore 7mm and a 3mm hooded vest and gloves and I froze...
Dive operators? As above.
We went with LovesParkScuba.com who is running a special on prepaid summer
Capt Dan Johnson has actually discovered a couple of the wreck that we dive now
dives