Do guys open their legs too?

It depends on what is being done to me. If she is giving me oral then sure I will open up my legs enough for her to have better access. I don't spread them as wide as most women I know can though. Just enough to let her in.

Yes when getting into different positions we do, but that is just because it is part of the position. I guess that easier access falls in there too.

Guys do it too I've found especially when they are receiving oral sex.

When they're laying down, they open them slightly. probably to allow easier access, but they don't open them really wide like a girl would. It isn't necessary.