You can be summoned to Thrallmar/Honor Hold by a warlock.
Yes, you can. However, you have to remember that many warlocks won't do blind summons. Keep those requests to your guild or your friends list.
Here's what I posted on the subject on the Main forum:
As a warlock, I don't do blind summons. If I happen to be in a group with two other people and a free slot, I might summon them to wherever I happen to be at the moment (and they might not like it if I'm in the middle of the bone wastes), but I'm not going to go out of my way to return to Shattrath just to summon someone. I'm also not going to go out of my way to gather two other people to group with in order to perform a summon.
Extra gold doesn't make a difference. Between all my toons put together, I have approximately 4K gold, so adding an extra 5g for the summon is insignificant.
But, I do summon. I'll summon guildies and anyone on my friends list. I'll go out of my way to perform those summons, because those are important to me. Getting a stranger (and a lowbie stranger, at that) to Shatt is so far down on my list of priorities that I could hit page down for 24 hours and not find it.