To follow on from Rob’s very informative post above. Please don’t be tempted to ignore the suggested route, and travel through Pwllheli town to get to the Eisteddfod, unless you really have to!
Pwllheli is a small town which serves as the main thoroughfare for the rest of Pen Llŷn with narrow roads, one-way systems and no bypass roads at all.
So all the regular tourist traffic in and out of Pwllheli itself to Abersoch, Aberdaron and the rest of Pen Llŷn is famous for bringing the town to a complete standstill.
I grew up in Pwllheli and later lived in Mynytho at which time we only went into town during the day if we really had to, and if we couldn’t get grocery deliveries, we’d go shopping in the evenings. Out of season, it would take just 10 minutes to get into town from Mynytho, during the holiday season it took 30 minutes and parking was a nightmare.