How long to wait before cleaning new tuckpointed brick mortar with muriatic acid?
I would scrub with water only @10hrs - 48 hrs.

I wouldn't use muriatic/water until 3-4 weeks. Be sure to add acid to water, not water to acid.  An 8:1 (water-acid) mix is a good place to start. 

Pre-wet the wall and any plants nearby. Rinse off then neutralize with ammonia or baking soda and water.

Old clothes, rubber gloves, eye protection.  If you use it any more concentrated, organic respirator.