I have a document stating "Set up your ad before 30th June, 2012 and we'll give you $75 in free advertising." with the document is a coupon saying: "offer expires 30th June, 2012" does this mean I should use all the credit before 30th June or just set up before 30th June. It seems ambiguous to me.
Welcome to the forum
Harry is correct. There's always an expiry date with the promotional coupon you get via Adwords. You have to redeem that coupon before that expiry date otherwise you won't get benefit of free voucher. See this for details.
So if you have the coupon, redeem it and set up your account and start advertising on Adwords. Remember to include the billing details, but you wont be charged until the coupon is used up.
Let us know if you need further assistance regarding Adwords.