Technically speaking all animals entering and leaving the USA need to be inspected at a designated port. Inspections cost $50 for none CITES and $75-90US for CITES animals. The inspecting officer may or may not charge you for an inspection since you are carrying them as pets (it'll all depend on his mood). How many corn snakes are you talking about? If it is just a couple hopefully they don't hassle you too much. If US Customs catches you trying to "smuggle" animals into or out of the US they can fine and/or throw you in jail. So, if it were me I'd call them to tell them you are comming to setup an inspection at both ends. If they confiscate the animals they will most likely be destroyed.
Just for everyones knowledge to bring animals into or out of the USA one needs a valid US Import/Export permit. This costs $50 and is valid for 1 year. All animals must be imported and exported at a designated port (their are 13 of them.......such as Miami, Chicago, LA....etc). If you cannot go through a designated port one can apply for an Exemption to Designated Port Permit which costs $25 and is valid for 2 years. It takes 10-14 days to get both permits. Once you have those permits you are allowed to import/export animals into/out of the USA. Inspections must be booked 72 hours in advance and you are charged anywhere from $50-90 depending on type of animal.
What I described above is what you need to legally import/export animals into/out of the USA. For "pets" sometimes customs will bend the rules for you and sometimes they won't. So, to avoid any delays, fines or jail time I'd advise to call US Fish and Wildlife to see what you are going to need to do things legally.
I hope this helps,