Is it safe to ride a rusty bike?
It is of course much better to ride a bicycle that's completely rust free. However as long as the rust isn't affecting the integrity of the bicycle you should be fine. That said, if there is rust on your chain, shifters, or other moving parts, you likely will find the bike a bit harder to ride and pedal. If your bike is so rusty, that things are starting to fall off, you probably should take a break.