Difference between 两个都 and 我们俩 Pimsleur's Mandarin course teaches 'both of us' as 我们两个都 (wǒ men liăng ge dōu), but in another question I asked here I recently found that 我们俩 (wǒ men liă).

Are these always interchangeable, or are there any rules concerning when to use one over the other? Are there any more ways to say 'both of us'?
俩 means 两个and is typically more colloquial. 俩 is often used for people, but doesn't need to be. Some examples:


买俩馒头: to buy two steamed rolls
兄弟俩
他们俩。


Alternatively you can use "咱俩" in oral language, "咱" means "我". The difference between 我们 and 咱们, is that 咱们 includes the listener. So 我们两个, 我们俩, 咱们俩 and 咱俩 all mean "the two of us".

A side remark: when a father talks with his son he can use 咱爷俩 referring to himself  and his son.