Do you have Time Machine or "clone" backups of the Pro on a USB drive? If so, that's your best bet, by far. See How do I set up a new Mac from my old Mac or its backups?
If not, get the Ethernet adapter. Apple's is $29: http://store.apple.com/us/product/MC704ZM/A?fnode=MTY1NDA3Ng&mco=MTk0MjUyNTE
others may be available locally.
How long it takes depends, obviously, on your wi-fi connection and how much needs to be cloned, but, yes, unless you get the ethernet adapter, wi-fi is your only option. But listen to Pondini. Although Migration Assistant allows you to copy straight from the Pro, cloning from a Time Machine copy is more reliable. If you have such a copy already, use that. If you don't, try copying from the Pro. If it fails (and if it's going to fail it should do so within an hour or so, don't let it drag on), make a Time Machine copy and use that.
Warning, if you've never made a Time Machine copy, that *will* take a few hours. So set it up and let it run while you're at dinner or something.
Let us know how it goes!
I am going to vote here for use of the Time Machine backup. I just migrated everything from an iMac to a new Macbook Air, and in preparation I had purchased the little USB-ethernet adaptor. But when carefully following the steps for Migration Assistant (was actually doing this with Setup Assistant) using an ethernet cable between the two machines, the process just seemed to get stuck fairly early on (before even the menu of choices of what to migrate came up). I called Apple Care and they urged me to use the Time Machine backup instead. Luckily the Time Machine backup disk had both firewire and USB 2 ports, so I used the USB 2 connection and the Migration/Setup Assistant ran quite quickly, maybe 45 minutes or so to migrate about 100 Megabytes.
If you don't have a Time Machine backup (seems like everyone should have one of those), I suggest you purchase a 500-MB or 1-TB low cost external USB drive (under $100, some on sale as low as $50) and do the Time Machine backup and use it to migrate to the new system. If your older computer is running 10.4, then Time Machine is not available but you can download a free version of SuperDuper, clone the older computer's hard drive, and then use that clone/backup to migrate to the new machine. Doing the initial backup with either of these methods is likely to take on the order of an hour for each 150 Megabytes being backed up.