Just so you know, you really can decline the hep lock when you go in. They might give you a hard time about it, but in the end, it is your decision to allow it or not. The hospital where I am birthing this time does them as a routine thing, like most hospitals, but my MW says that her clients almost always refuse them.
I have every intention of refusing the hep lock unless/until there is some reason to think that I am going to need an IV. This did happen at my last birth b/c of persistent vomiting -- I couldn't keep any liquid down -- and it helped, so I'm not going to speak against them universally! And there's no doubt that if you do need an IV, the hep lock makes it much easier. But the hospital staff were perfectly capable of puting an IV in at the point at which I was clearly dehydrated and needed it. (Aren't medical personnel trained to insert IV's when people are dehydrated? I mean, isn't that what an IV is for, anyway?) I hated having it in my hand, though, especially because they took hours to remove it after DD was born, even after several requests. I finally had to threaten to remove it myself before they took me seriously. It was really uncomfortable for me. I know some people say it's no big deal, but it was for me.
Physiological birth does not require IV fluids, as a rule, so why should yours? Just keep eating and drinking through your labor and you should have no need for the hep lock. If this is against the policy of the hospital, bully your HCP into writing "food and drink to be allowed at all times during labor, no hep lock or IV" or something like that, on a prescription pad, signing it, and giving it to you. That way you can give it to the hospital when you come in, and let them figure out how to get around it!