I've owned 2 peach faced lovebirds (at seperate times).
If you want a companion, definitely go for one. The best place to get a companion parrot is from a breeder who hand-feeds the babies. I hand fed one of my lovebirds myself, but I don't reccomend doing that unless you have proper research and training.
https://www.birdbreeders.com/ is a GREAT place to look for breeders in your state. HOWEVER, since you said you're going to a bird expo, just ask the breeders if they hand-feed and how tame their babies are.
If you want them for show, go with a large flight cage, and two to keep each other company. However, you should go for an already bonded pair as 2 unknown lovebirds can and most likely will kill each other, and there's the huge hassle of quarentine.
18x18x18 is a bit too small... mine always had a 20"w x 20"d x 57"h on a stand. It was JUST like this one, but a different brand:
Hana Hut Playtop Bird Cage - Parakeet Bird Cages and Bird Cages at Bird Cages 4 Less
For diet, I would go with pellets, nutri-berries and plenty of fresh fruits and veggies, which is what my lovebirds both ate. The best brand of pellets is Harrison's. They're expensive, but organic and extremely healthy. Roudybush is another great pellet brand. Avoid pet store seed blends like Kaytee and Bonanza. Those types should only be used as treats.
The bird should have at least 5 toys in the cage, wood and leather are best, to play with, chew on and entertain them. You should change one every 2 weeks to keep them from getting bored with them. Another suggestion is: get a happy hut. They're little huts for the bird to sleep in. My birds were both obsessed with theirs. They should also have different types of perches. Wood, rope, and natural wood are awesome. 1 rope perch is needed so the wood doesn't hurt their feet. You can also add things like ladders and swings.
You need to clean the cage every 1-2 days. Most knowledgable parrot owners do it everyday. I used paper towels for the bottom; they're very easy to change out. If their perch or ladder gets dirty, just clean them off with soap and hot water. Make sure all the soap is off when you do.
If you get a companion bird, they definitely need at least 1-2 hours of companionship every day. They're flock birds, and they love their flock. Parrots are prey animals, so always use positive reinforcement and never negative. They very easily lose their trust and it's very hard to get it back.
A note: Primal Rage did make one good point. Don't pay too much attention to them as babies (as in overly cuddling them and paying attention to them), or they will crave it as an adult. That's JUST what happened to my second lovebird. I paid a lot of attention to it as a baby, especially because I hand-fed it myself. Then it started chirping and screeching for me all day, and with my hectic schedule and school work I couldn't give her the attention she needed, so I gave her to a parrot sanctuary. I had her for almost 2 years. She flies with a flock of lovebirds now though, and I'm going to try and visit her soon
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