When I upgraded to Heart of the Swarm I noticed that it automatically sets Heart of the Swarm to be your default playing level when playing multiplier and ladder. How do I switched back to WoL when playing with friends without HoTs? How do I switch to WoL to do solo laddering?
When playing with friends who do not have Heart of the Swarm, similar to when you are playing customs to those who do not have the full version of WoL, battle.net will automatically restrict you to WoL content.
To switch your default expansion level you need to access options from the menu tab at the bottom right hand side of the screen. In the options screen you then go to game-play options and you can choose the expansion level from a drop down box there.