A factory reset won't wipe the memory card, just all apps and their data (which includes phone numbers, texts etc, as these are technically application data). So your card contents are safe (apart from any apps moved to the card, which will still be erased).
If you can back up other data to your card you can restore them after the reset. I think the contacts app ("people") can export its phone book to the card - I know the standard Android one can, so I expect HTC's version can as well. Won't help now, but might in future. Are you sure your contacts aren't backed-up with Google anyway? That's the default, and if so they should just reload after the reset.
In fact, checking the old HTC manual (I've not had HTC software on mine for 18 months, so forget these things!) I see that it has a "back up my data" option under Settings->Privacy, to back up your data to the card. You could check whether that is set, and try it if not (assuming it's still there on more recent software)
Another thing you could consider before the reset is to install an app called MyBackup. This can back up a lot of application data to the card. The app will be erased by the reset, but if you then reinstall it afterwards you can restore the backup.
Your card contents should survive a factory reset, but to be certain it should be straightforward to back up the card contents to a mac. Just connect the phone to the computer and select "disc drive" on the phone screen. This will then make your card look like a USB drive on the computer, and you can then just use the Finder to copy stuff from the card to the Mac (or terminal commands, if you're like me
). What is saying that you need to download software anyway? As long as you select disc drive mode you should not need to download any software.
Unfortunately I can't suggest sync solutions for a mac, as I've never synced my phone to a computer - I just sync calendar over the air with google, and the rest I back up to SD and occasionally back up the card to my computer.
