While Tagalog is spoken in Baguio, the city's lingua franca is Ilocano.
You may get more help and enthusiasm and maybe discount price, hehe) if you'll learn Ilocano.
Not everyone in Baguio and from Baguio are proficient in Tagalog either. Some Ilocano speakers (esp native Igorots) are more able to express themselves in English than Tagalog.
Just go the the market, jeepney stops and you'll notice that most people speak with each other in Ilocano.
I remember having a conversation with a "sekyu". His spoken Tagalog was poor, and my spoken Ilocano was poor. He spoke to me in Ilocano, I responded to him in Tagalog. We still understood each other though.
You'll just have to adjust your expectations and "strategy"
I have to add, the Tagalog spoken in Baguio is slightly different than standard Filipino given that locals use a lot of Ilocano words and sometimes Ibaloy and Kankanaey words like ngay, ngarod, adi, piman, ta, kwa, gamin, etc..in their Tagalog
So yeah, temper your expectations
Next time, say "Naimbag nga aldaw" instead of Magandang Tanghali. People will be more thrilled. No one even uses magandang tanghali in Baguio. It's always the accented "gudapternun mamsir" or naimbag nga aldaw (formal occasions, usually)
If you want to truly practice Tagalog, moving to Batangas/Cavite/Laguna/Rizal might be more ideal since these are the "core Tagalog territories".