RP on Wyrmrest Accord is partially guild-based at the moment, but there’s also quite a lot to be found in the way of public events and open campaigns. So, while random walk-up can be tricky to find outside of a few specific places and timeframes, there’s certainly RP going around that doesn’t require you to be in a guild.
For Silvermoon City in particular, you just missed an event that was held a couple Sundays ago. If you’re free and interested tomorrow evening, however, another event is being held in the garden area outside the Shepherd’s Gate. You can find a post about it here.