Yeah, not knowing much about the original material, it didn't even cross my mind that Deadpool could be anything but heterosexual. Because his humour is very... bro-y. I took those as "gay panic" type of jokes.
As for the film itself.. when it's funny it works very well (the opening credits are a highlight), but I found it pretty dreadful when it decided to tell an actual story... without ever actually stopping to build any semblance of a character. Morena Baccarin is playing a male fantasy on legs, and I found the whole relationship unengaging at best.