Is it safe to carry laptop around in sleep mode?
Solution 1:
I've been doing it (carrying a sleeping machine around in my hand, backpack, trunk, etc...) with Apple laptops for years. Going back to my powerbook 190cs in the early 1990s.
No trouble.
Had a few PC laptops in there, too and treated them the same way also with no trouble. Note that "sleep" means slightly different things in the two cases, though.
Solution 2:
The danger comes from jarring the laptop while the hard disk is spinning. It's highly likely that the hard disk spins down in sleep mode, as it's one of the chief power consumers.