In reply to La benya:
> If they ask you to climb, say you would love too, but you've popped an A2 pulley and cant.
If you go with this, you run the risk of not being able to do enough to blend in well. So, if you do (or, to be fair, if you don't, as it can only help either way) make sure to compliment your girlfriend and her father on their climbing - "nice send dude" works well, and if you think that it's particularly impressive, a fist bump is probably in order. If it's
really impressive, accompany this with a mouthed "pow" and a slowly-opening-hand-signifying-the-send-being-so-cool-that-it-just-blew-shit-up gesture. This kind of behaviour will make you seem like a properly old-school climber.
Some other thoughts:
If you're bouldering, or if someone is leading and hasn't yet placed a piece of protection, 'spotting' is useful - it means that if the climber falls, you can prevent them hitting their head if they fall over. Scream "spoons not forks" over and over, in a kind of mantra, so as to remind yourself that your fingers should be bent like a spoon, rather than straight like the tines of a fork.
If your girlfriend or her father are leading but haven't taken all of their gear with them, practice placing what's been left in the features of the rock at ground level, as this sort of engagement will really sell your interest in climbing. Some tips for this include: Make sure that placements are as far back in cracks as possible for maximum security; cams (which consist of semi-circular lobes that can be retracted using triggers) should be put in the snuggest cracks that you can find, so that the trigger is pulled all the way back and you still have to push/wiggle a little to get the cam in; slings aren't super useful, but if you drape them on ledges they can look quite nice and give dull, grey rock a bit of colour.
Climbers are quite a boisterous, un-PC lot, so if your girlfriend or her father are looking a little wobbly or nervous while climbing (happens quite a lot, as it can often be scary!), don't be afraid to encourage them with some banter - crude stereotyping based on race, gender, sexual orientation, political leaning, or social class is all good stuff, and will make everyone else at the crag laugh along with you.
Hope you have a great day!