Combination locks really are terrible, always go for a key lock. I was shown the technique for unlocking combination locks by a lock expert and it really is simple. It is also quick to do on anything but the more expensive locks (but even then I've broken into an expensive combo lock for a friend who'd forgotten their code).

That said, I was also shown the technique of using shims to open key padlocks too which was equally quick with the right tools so best advice is to leave nothing but clothes for the tea-leafs to find.