Either one sounds correct to me. I am more like to say "I could also..."

'Too' and 'also' have the same meaning. The only difference is that while 'too' has to go at the end of the phrase, 'also' can go in other positions in the sentence. Here are some examples. 'You could play football this afternoon. You could play tennis, too. This is the only position that you can put 'too' in. It must go at the end. But if you want to use 'also' you could say: 'You could play football this afternoon. Also, you could play tennis. 'You could play football this afternoon. You could play tennis, also. 'You could play football this afternoon. You could also play tennis. In fact, the only place where you can't put 'also' is between the main verb (play) and the object (tennis). Native English speakers would never say 'You could play also tennis'. This is a common word-order error which non-native speakers make. Remember to keep the verb and its object together in the sentence. Of the three options above, the most usual one is the third sentence ''You could also play tennis.' If you don't know where to put an adverb, the most natural position is before the main verb, 'play'. For example, in other tenses: I'm also playing tennis. I'll also play tennis I have also played tennis. This is also the most natural position for other adverbs, such as adverbs of frequency. For example: I could often play tennis. I could usually play tennis. I hope that helps.

There is no significant difference between "too" and "also". They mean the same thing, but "too" is used far more often. "Also" can sound formal, but it would not be wrong to use it. As for the question, in casual conversation, either one would sound just fine. The grammar rule is that you never want to split the verb. For example, if you want to say "I could eat," you would put "also" at the end ("I could eat also") or before the verb ("I also could eat"). In English, "could eat" is the verb, and you do not want to split that up.

Thank you Ibrahim!

I disagree with "too" only going at the end of the sentence. For instance, "I too speak Spanish" is perfectly fine (some may wish to throw in a comma or two in there, but not essential)