This (IMHO) is an instance where use of the term 'partner' may not be sufficient and could lead to confusion. Bear in mind that term it isn't as commonly used in the US as it is here. Accordingly, if the reply to 'what is the purpose of your visit' that's typically asked at immigration is 'to visit my partner', there may be a blank stare or a further question about intention to work.
If you are married, a return ticket and knowledge of immigration controls in the US are usually sufficient. If an unmarried couple, a return ticket and some indication of available funds, plus just being truthful and stating 'a 2-week visit to see my friend/girlfriend/boyfriend/significant other (or whatever) is sufficient. Anything else that indicates intent to return home might help, but isn't generally required. Basic rule is just answer the questions in a straightforward manner, and as succinctly as possible. Don't offer more than is asked for.