Learning Brazillian Portuguese

Every Monday and Wednesday afternoon Marina, a language teacher, comes to teach us Brazillian Portuguese. These classes are alot of fun, as most of us are finding the language extremely difficult - especially trying to pronounce words correctly. The training we've had in other languages (Spanish,French) helps us with understanding the written word but hinders us in interpreting what we hear, or when we try to speak Portuguese with the correct pronounciation. I tried to learn some before I came here, but it didn't seem to help.
Some interesting things about Brazillian Portuguese:
"T"s may be pronuonced "che". At the Orphanage the kids all call me Tia (means aunt) but it is pronounced "Chia". Other times "t" is said like "tea". I haven't figured out when to say "che" versus when to say "tea".
"D"s may be pronounced like our "g", other times it sounds like "dee". When I am with the kids I often say "divida" (which means share) and it is said "giviga". No wonder they looked at me strangely the first week.
It is also hard to know which syllables to emphasis, what is silent etc.
During orientation we were told to tell taxi drivers to take us to the "Graca McDonalds" as it is close by, there is only one in this area, the taxi drivers will all know where it is and there'd be less of a chance that drivers would misunderstand us. Well this didn't work for any of us for the first 2 weeks because "McDonalds" is actually pronouced "MackeyDonalge". We are now getting home quicker and dropped off closer to the Home Base. I'm going to recommend on my evaluation that they teach this first.
Tchau (Bye)!