[Dem]

(01-21-2015 04:31 PM)one-two Wrote:  

"[let's] hang out and get a drink this week"
Давай встретимся и выпьем на неделе
This does not sound right, because "a drink" translates as "to drink" and Russians don't believe on moderation.

Давай встретимся и выпьем на неделе. ==> Such an expression is valid if you want to invite a old military friend in order to commemorate the dead comrades. In regard to the girls it's going to sound vulgar, but if she is a chav or an alcoholic then you may do it.

(01-21-2015 04:31 PM)one-two Wrote:  

"let's have some coffee [Thursday], there is a park nearby"
Давай сходим на кофе в четверг, там рядом парк есть.
This also sounds a little soft, but I can't think of anything more clever.

The preposition "на" is not appropriate. You can say: Давай сходим на праздник... (Let's go on holiday to someone else) or Пойдем на день рожденья к ... (let us go birthday to...). The preposition "на" is used when you mean any event. So you need to just say: Давай в четверг сходим в какое-нибудь кафе где рядом есть какой-нибудь парк (Let's go down to some cafe where near is any park.).