You will find that running the co-ax under the velcro flap on the 'curb' side of the trailer is the best solution, IF you place your TV on that side of the trailer. That is the way we handled it, too.
(Addition 4/8/02) If you trace the wire coming from the antenna, you'll find it comes out of the top half, runs externally down one of the arms on the street side, and back into the trailer from underneath. At one point, on ours, I found a "barrel coupler" connecting the lead coming from the antenna to the lead going into the trailer. The cable has 'F' connectors (screw-on type) on all end. You can get a "T" connector at Radio Shack (under $5) and insert it at this point, which effectively give you a connection on the outside of the trailer to connect park TV service to. Carry a 25' extension with 'F' connectors on both ends and you'll be set.
Regarding the Winegard signal amplifier, I found that when attached to a cable system at an RV park, I had to turn the amplifier off, because it 'boosted' the incoming signal too much, causing gross distortion of the picture. The amplifier is intended to 'boost' the signal from the antenna only, when you are in 'fringe reception' areas.
If you use a satellite dish, as we do now, you need to find another way to get the signal from the dish to the TV. Because of the signal and voltage used in the sat. system, the Winegard amplifier board (in on or off position) will not allow the dish signal to pass. I'm installing a cable in my new trailer exclusively for the sat. system. :
I hope this add'l information is helpful.