Children can learn languages fast. However, children will use whatever means to communicate themselves with people. So if your child has a friend that only speaks Spanish, he/she will try their hardest to speak a word or two to them. That being said your husband should only speak Spanish to your child. That way your child will realize that Spanish is the only way to communicate their ideas to their dad :) Tv shows in spanish help alot too.
It would also be a good idea to enroll your child in a bilingual class at school if available. If in the outside world you child surrounded by english, you should try your hardest to only speak Spanish at home. This is also a great way for you to learn some Spanish too :) Your husband can give you vocabulary words to learn, and everyday in your daily activities you and your child can apply them.
Also any books,music,tv should be completely in spanish since your husband isnt home alot. If faced with pure spanish, your child will quickly pick up on it~ Good Luck!
Native spanish and english speaker, having trouble since my brothers are living in a English-only environment. Since trying these methods, they have increased theie Spanish usage and vocabulary ^ ^