Can you attack twice in one turn?
I would say that player characters are capable of attacking twice. The rules state you have 2 Actions to spend each turn, spent on a list of actions that cost 1 Action each, with no further limitations beyond the cost.

This is reinforced when they explicitly state that this option is not available to Monsters, a case of "the exception proves the rule".

I.e., "no free parking on Sundays" implies parking is free every other day. Monsters can't attack twice (without stating otherwise for players) implies Player Characters can.