HTTPS works fine for me?
curl https://api.mercadolibre.com/users/1
{"id":1,"nickname":"NICTRAFFICGENER1","registration_date":"2011-09-05T12:00:00.000-04:00","country_id":"CL","address":{"state":null,"city":null},"user_type":"normal","tags":["normal","test_user"],"logo":null,"points":0,"site_id":"MLC","permalink":"http://perfil.mercadolibre.cl/NICTRAFFICGENER1","seller_reputation":{"level_id":null,"power_seller_status":null,"transactions":{"period":"historic","total":0,"completed":0,"canceled":0,"ratings":{"positive":0,"negative":0,"neutral":0}}},"status":{"site_status":"deactive"}}
python -c"import requests; print(requests.get('https://api.mercadolibre.com/users/1').text)"
{"id":1,"nickname":"NICTRAFFICGENER1","registration_date":"2011-09-05T12:00:00.000-04:00","country_id":"CL","address":{"state":null,"city":null},"user_type":"normal","tags":["normal","test_user"],"logo":null,"points":0,"site_id":"MLC","permalink":"http://perfil.mercadolibre.cl/NICTRAFFICGENER1","seller_reputation":{"level_id":null,"power_seller_status":null,"transactions":{"period":"historic","total":0,"completed":0,"canceled":0,"ratings":{"positive":0,"negative":0,"neutral":0}}},"status":{"site_status":"deactive"}}