I do it all the time. Most people I go watch games with aren't even aware I am betting on the game we are watching. Doesn't really make a difference to me. All of the people that really know me are aware I sports bet but it doesn't really come up unless they ask me about what the line is on a game. Usually if I have a big bet on a game I watch it at home so if there is an outburst no one else is around to here it if things go bad.
I actually find it funny when with a friend that has no idea about what the line is wants to make a bet. There is always some clueless guy willing to make me a bet on his favorite team straight up in whatever game even though his team is a 8 point dog.