Congratulations!! You have discovered that on the subject of oil, EVERYONE has an opinion. Try getting help on an arcane subject, and very few will even bother to respond.
Anyway, when I lived in Glendale and drove at the track in the high desert, where temperatures of 110 are not uncommon, all of the guys in the club were using 20W50 with no ill effects. And since it is difficult (if not impossible) to find something like 10W60, you can do no harm with the 20W50. It will protect you at 110, and will not gum up at 32.
So good ahead, enjoy your MB without the Fear of Driving; it doesn't really matter what brand you use, as long as you change the oil every 3,000 miles.
See other posts (using the search feature for "oil", and you'll see 1000s more opinions.