While it's very understandable to want money in lieu of gifts, it's very tacky to outright ask for it. Having a Honeymoon registry is an excellent way to go about it or you can have close family and friends spread the word that you would prefer money (this way you don't have to mention it yourselves to more extended family or friends). I've found that anything I tell my MIL-to-be or grandparents is spread very quickly through the family.