I am taking a three day trip starting on March 9 to visit my brother who lives in Altamonte Springs. Do you guys have any suggestions as to budget-friendly Disney alternatives in the Orlando area and its environs? Previous activities I've already done are:

Disney: Magic Kingdom and Hollywood Studios

Wonderworks

Wekiwa Springs, kayaking and swimming

Seeing the manatees

Morse Museum

Downtown Disney

Walking around Winter Park and the boat ride

Gatorland

Walking around Sanford

Lake Eola park

Peabody ducks

New Smyrna beach

Sea World

Islands of Adventure

Thank you!

if you have a car how about Kennedy Space Center?

Yes, we have a car!

Brevard Zoo is one of my faves, it's near by and their Zip Line course is lots of fun too.
https://brevardzoo.org/
http://www.treetoptrek.com/

Orlando Science Center is terrific.
http://www.osc.org/

Do you have kids with you? Ages?

No just me and my brother. We're 24 and 32.

Just last year we had an incredible "old Florida" day doing two things in early March:
1. Eat breakfast at the Old Spanish Sugar Mill that is inside the Ponce de Leon Springs park. It's an old mill that is now a restaurant. There is a grill in the middle of each table and you cook your own breakfast food. It's a blast. You will want to get here very early on the weekend when waits can be 2 hours or longer by mid-morning.
2. Rent a pontoon boat at Hontoon Landing Resort & Marina and spend a half day puttering down the St. Johns River to Blue Springs. We did find that the 4-hour "half day" rental wasn't quite long enough and vowed to do the 8-hour the next time.

I've lived here my whole life and had never done either of these two things. Doing them in one day was great because they're close to each other. You will want to get an early start to do both together.

I did just note that you had already mentioned seeing the manatee in your list...so you've most likely been to Blue Springs. But arriving by boat is another experience entirely. And we have NO boating experience...so you'd be fine I'm sure.

It's about 35 miles to Lakeridge Winery and Vineyards in Clermont. I am not certain if it's still free, though. Have you guys been to Spook Hill in Lake Wales? It only takes a few minutes, but it's crazy. You park your car at the bottom of the hill and it moves up on its own.

A bunch of Major League Baseball teams are in Spring camp around Orlando if you like Baseball . . games are usually pretty easy to get into. As above, Kennedy Space Center is a hop, skip and a jump

Kennedy Space Center is a great idea. Spook Hill is funny if you're already in Lake Wales but not worth a trip on its own

Do you have any interest in Frank Lloyd Wright? Florida Southern College in Lakeland has several FLW structures and a variety of tours, including a self-guided free one: http://www.flsouthern.edu/fllw-visitors.aspx

Rivership Barbara Lee
http://stjohnsrivershipco.com/

Bok Tower Gardens
http://boktowergardens.org/

Boggy Creek Airboat Rides
www.bcairboats.com

OR

Twister Airboat Rides & Lone Cabbage Fish Camp
http://www.twisterairboatrides.com/
They are located on SR 520 where it crosses the St. Johns River.

_____________________________________________
Vic's travels: http://my.flightmemory.com/vogilvie

Bike week is on and there are races at the speedway in Daytona with great infield activities. Main St is fun and Destination Daytona will be having bands and things to see.

Spring Training games also!