Hi J.,
No, I do not think that 19 months is too young to use the potty. Personally, I think that it is better to introduce the potty earlier vs. later, but I wouldn't expect a child your daughter's age to be 100% potty trained in a few weeks, either. When a child is this young, the parents have to be "trained" a little, too. :-)
One thing to keep in mind is that there are different mindsets and schools of thoughts when it comes to potty training. None of them are "right" or "wrong", but it really depends on what your expectations are and how much time you and her other caregivers have to devote. What I state below is my own opinions and experiences...
To your arsenal of potty supplies I would add some "training underwear". They are thick, padded underwear, and you won't have the mess you will with regular underwear. I think at this point, you still want something that can absorb accidents, but you also want her to feel when she is wet. I would hold off on regular underwear because I think they set the bar too high at first, esp. w/such a young child. You might be cleaning up too many messes of the floor and get frustrated! Another option besides/in addition to training underwear is cloth diapers. They have come a long way in recent years--there are even "all in ones" that look just like disposables, no fancy folding or anything. Pull-ups are just basically expensive diapers. They are good for when you are out and about and at nighttime, but they tend to just delay things.
I'm not sure what the travel seat is, but besides a potty chair, I would have a toilet ring that goes on the regular toilet. My son won't sit on a potty chair right now, only on the toilet. It's good to have a few options on hand, in case your daughter gets fickle!
To kickstart this, my recommendation to you is to devote 1 or 2 whole days to getting used to her potty rhythms. If she's been in disposables, you probably don't know *exactly* when she poops or pees. If possible, let her go naked from the waist down. If you have carpeting in your house, put some training underwear on her. Block off a room or two that you and she can play in for a few hours at time. Have the potty chair right there. I would recommend having her "try" every 20 minutes. You will start to notice patterns--she will probably pee x amount of time after a meal or snack, and she will look a certain way right before she goes. (Some kids stop and sort of look like they're daydreaming; others may start moving quickly like they are agitated.) A GREAT resource for getting in tune with your child's potty habits is diaperfreebaby.org.
As for my own experience, my son has been using the potty since just before his 1st birthday. (He is now 17 months old). I don't say he's "potty trained", only that he "uses the potty part-time". He goes # 2 almost exclusively on the potty. (The exception is if he wakes early in the morning and goes in his diaper before I get him.) I am pretty in tune with when he has to go pee, and many days we only have 2-3 wet diapers to deal with--the rest of the time he is going on the potty. He knows the sign for "toilet" and often will sign it and start running towards the bathroom when he has to go. He is still in cloth diapers--I don't think we're quite ready for training underwear just yet. I don't mind having to assist him in the bathroom, and I don't expect him to be "potty independent" for quite some time. He still needs my assistance for everything else (dressing, eating, walking up stairs) and just like every other area of development, he will slowly become more and more independent.
Good luck to you, and feel free to email me if you have any questions for want to chat.