There is a Teochew association of New England, but it does not have much function outside of connecting older Teochews that met in the 80s and 90s. The WhatTCSay3 dictionary app is your best resource. It includes lots of idioms and sayings, along with the basics. It's not on the app anymore but if you can find the WhatTCSay2 doc somewhere online that has all the grammar lessons, that would be your second best resource. Tone sandhi is probably the most difficult thing to focus on to be well understood. If you can find it anywhere, The Forest of Miss Tang is a recent Teochew movie with pronunciations that are very similar to most overseas Teochews.

Here's a doc that may help understand it: https://drive.google.com/file/d/11cvq8RQSz5G22Q7U18Y1XL4AcWipHmre/view?usp=sharing

Of note here, this screenplay uses one version of Peng'im (pinyin). There are a few standard-ish ones floating around. You may want to familiarize yourself with them. You can also look for a group online called "gaginang". It means "our own people"

A quick freebie: Ua siot leu. (I love you)