My Master's thesis was a review of Spanish-English dictionaries. Based on my research, I cannot recommend the Simon and Schuster's International.
On the plus side, it does have a large lexicon, and on occasion I have found a word in it I found nowhere else. But the dictionary's problems are many.
Its lexicographic technique is, to say the least, inferior. Take for example the English noun "Spring": "1. muelle, resorte. 2. rebote, elasticidad. 3. (fig.) elasticidad, vigor, energia. 4. fuente, manantial. 5. (fig.) fuente, principio, origen. 6. salto, brinco, corcovo. 7. primavera. For the English speaker writing in Spanish, this is hopelessly inadequate, as the dictionary provides no clues as to which word to use in which context.
Compare the treatment of the same word in the far superior American Heritage Spanish Dictionary: "(coil) resorte m, muelle m; (resilience) elasticidad f; (jump) salto; (fountain) fuente f, manantial m; (season) primavera; (source) fuente, origen." This is far more useful, as the dictionary provides glosses in the native language to guide the user through the choices.
A second problem with the Simon & Schuster is its poor organization. This is important in large desk dictionaries. In an entry for a complex word like "get," the Simon & Schuster forces users to lose time searching for their translation through unbroken columns that extend for more than a page.
Third, a good dictionary should maintain an up-to-date lexicon, including such cultural and technological additions to the language as "baby sitter," "hostile takeover," "software," "flash drive." The Simon & Schuster Dictionary is mediocre in this respect.
It has many errors, including some with false cognates (words that appear to mean the same in both languages but do not) and wastes space on unnecessary definitions.
The Simon & Schuster fails to live up to its claim as an "Intermational" dictionary. While its treatment of Spanish regionalisms is scanty, the depths to which it is bound by its American origins and fails to cover British English makes its title a mockery.
Due to its wide coverage, some users may find reason to add this work to their collection of Spanish-English dictionaries. But as a user's only dictionary, it is a poor choice. Oxford, Collins, and Larousse offer large dictionaries which do much better on all of the issues mentioned above. Most users should buy one of these instead.