Latin American Spanish vs Castilian Spanish

I did just fine with the Spanish I learned in school in California---so Mexican Spanish. My boss, who is Mexican-American and fluent in Spanish ( his first language) visited Spain with his wife last year. He said he tried to adjust to the Castillian pronunciation and was told (kindly) his effort was appreciated but they would understand him better if he just spoke his usual way!

In Barcelona, the language is Catalan, not Spanish. You might do better with English than Spanish there.

As a native "latin american" speaker I had no problem at all speaking and understanding spanish in Spain. My sister and her siblings live there and they also never had any issue.

As my "latin american" spanish is a bit slower in my native reagion, I always make myself express well but in rare situations as "Spain" spanish is a little faster and close spell (to my ears at least) I might miss a few words when listening.

There are also what we call "modismos", that are characteristics phrases of each country or region. That can take a little while to catch up, but it is of minimal impact in communication (at least for me).

I believe you would not have any problem at all with your "la" spanish.

Buen viaje para tí, Oleee!

Yes, it will be fine. From my understanding, advanced but not fluent speakers occasionally have trouble with high level stuff. Basics are fine. I learned the little Spanish I know from Mexican teachers and practice with Mexican-Americans. I have no more difficulty in Spain than with them. Be aware that the vosotros verb form will be used (no need to use it yourself), and that in much of Spain z is pronounced more like th. So words like zapatos or cerveza will sound different. Use the pronunciation you know, but in listening be aware.

I've only been to Barcelona, so I can only comment on that. I used my patched-together southern California high school Spanish and people seemed to understand me. I was nervous at first about using it as I'd heard that I need to speak Catalan there, but I made a few tentative forays and people were totally nice (and probably amused by my syntax errors!). It made traveling in Spain much more relaxing than my usual destinations like Italy and France, where I am basically silent but for a few greeting words etc.

It's similar to a British person in America (or vice versa). Unless you are using specialized words or local slang, you will be understood just fine.

"hope that many people will speak some English too."

Change the "many" to "some," and you won't be disappointed or frustrated.

Be aware that what we call "Spanish" is called "Castillian" in Spain. I had no problems using my Castillian (such as it is) in Barcelona; people were happy to answer me in Castillian with no hostility or tension whatsoever. (It's not like using French in Flanders, which is indeed frowned upon).

I had no problem speaking my American-accented Spanish, but understanding Castilian can be extremely difficult for those of us used to the drawn-out "singsonginess" of Mexican accented Spanish. Just tell the person to whom you are speaking to "habla despacio, por favor" and you shouldn't have an issue.

You will have fun with Andalucian spanish! My husband, born in Bilbao and with Spanish as his first language had a bit of a time catching on to the Andalucian habit of dropping word endings. ("gracia" rather than "gracias". "Adio" rather than "adios".) Throw in the lispy "c's"and it in very rapid conversation it can be beautiful, but challenging! We especially noticed it listening to news broadcasts. Noticably easier to understand (at least to my ears) as we left Andalucia and made our way to Madrid. Enjoy your trip!

My Spanish ability is limited to 2000 words, more or less depending on how awake and caffeinated I am. It's also lopsided in that I speak much better than I can comprehend listening. Main problem was when the other wouldn't slow down. Google Translate came to the rescue or I tried another person.

Minor problem was in Barcelona. When I asked bilingual people for a word I only knew in English, they gave me the Catalans word. By the end of 4 nights there, I realized knowing the Catalans word was a gift because Barcelona es major!