Caernarfon is a good place too. I can recommend Caffi Maes.
Every time I've been in, they've been friendly. I think they would be very accommodating to Welsh learners. The top floor can get like an oven in summer, but I love their burger dishes - good portion sizes and I'm usually totally full afterwards! It's a favourite of mine in Caernarfon. Down some of the little streets there are interesting ice cream places as well.
Baruch, you must go to the Ty Hwnt i'r Bont in Llanrwst. There are teatime selections where you get a mixture of dishes. Me and my mum made the mistake of ordering one where it includes bread, scones, bara brith and a cake. I think it came on 2-3 dishes it was so big! We actually couldn't fit it all in, and all the tourists were staring at us! So, be careful what you order I guess because it's easy to order too much in there . The scones are very good, so stick to them in terms of sweet things. I'm not sure if you'll get to practice Welsh much there, but visit anyway. It's a gem.
Also, if you want to buy local produce, always look at the back if you want to make sure if something is actually locally made in Wales. Tourists often want something locally made when it comes to food produce especially. However, they often don't realise that it's very common for companies to slap on their own label on the front of a jam jar and make it look cute or cottage-style, but actually it might be mass produced in a factory in England. Also, I don't remember where you are from, but if you're buying honey, check first if you can carry it back to your home country on a place. Some countries have restrictions on this,