Great Question !!!! You should get tons of answers... I myself will be anxious to see what others have experienced...
Your Question:
Name 3 things:
1 thing you wish you had known before going to Costa Rica,
1 thing you wish you had brought and
1 thing you wish you had left behind
1.The level of illiteracy; especially in rural areas. I've been here long enough to see how much effects daily life... from the inability to read signs/direction/instructions; to chaos in 'waiting lines' and at Bus Terminals, to the 'shrugging off' education by teenagers whose parents didn't bother with it either (a sad and continuous cycle of a poor lifestyle); to how it contributes to teen pregnancy (like... 13 and 14 year olds) and incest. Ultimately, I can even see a sort of aloofness and accepted intolerance amongst the educated people, especially in any kind of service industry (health care, migration, banking, etc.) when they are constantly confronted with somebody who can't read nor understand 'big' words.
Look: Public education here isn't great... but it's free... and they should respect that because it is paid for by all taxpayers. I told a good friend that his son could NOT be a part of a work crew doing concrete work on my property because he had dropped out of High School... against the wishes of his parents. He, like many others, was too interested in riding his motorcycle and drinking and smoking.... since dropping out, he has had 3 accidents and lost 2 toes and half a finger and has become acquainted with hospital food; not to mention, blacklisted from jobs. I told 'them' that I didn't want to risk having somebody so irresponsible on my property when there is equipment involved. My friend is still my friend; and his son is learning some tough lessons.
2.Wish I brought but didn't ????? Hard to answer. I've found, over time, most of what I need here and have learned the alternatives as well. Example... 'Neobol' is the local alternative to Neo Sporin and is AMAZING. I think it is a healing miracle. Get the cream and not the spray. LOL!! Otherwise... Probably nothing. But more art would be nice. Most 'art' here is craft and is souvenir oriented or just cheesy and unsophisticated. I'm an art snob.
3.I brought a heavy bedspread and a few blankets... basically, I used them to 'pack' things that were breakable. But now they are useless as are the few sweaters that made it here... Where i live it almost never gets below 72 degrees. The sweaters went to a guy who rides through the mountains, regularly, to get to work via motorcycle because it is cooler up there. And the blankets?? I'm sure if I pull them out of their hiding places, they are starting to rot.
Pura Vida