Let's say that it's not all PIC that have at least 1 USART. But it doesn't mean that we are not able to do serial transfer. SERIN/SEROUT/.../DEBUG are a software solution. A USART is a hardware solution. AND it also provide a cute 2 Bytes buffer in.

with 2 USART, the first that spring to mine is this huge 18F8720... probably too big for what you want to do.

There's still some way to do it cheaper by using 2 PIC, and probably only one PIC with or without USART. But in this case, i couldn't figure it will be really reliable if there's no FlowPin control or an intelligent interrupt + SerialHeader combination... if possible.

Maybe the 2PIC solution is safer.