Let me start by fixing your initial sentence.
My take on translation:
I can speak Latin easily.
Latine facile loqui possum.
- You speak "Latinly", Latine, not "in Latin".
I do not recall seeing the preposition in in this sense in Latin, but I could be mistaken.
Nevertheless, the adverb (Latine, Anglice, Germanice…) is the typical way to express using a language in Latin.
- The verb loqui is deponent, so you need to use formally passive forms.
For example, it is loquor instead of loquo.
Next, I'll offer a completely different alternative.
It is common to express such things with the supine ablative.
My suggestion with an overly literal English translation:
Lingua Latina (mihi) facilis est locutu.
Latin language is easy (for me) with respect to speaking.
As brianpck suggested in a comment, this is another good option:
Facile est (mihi) Latine loqui.
It is easy (for me) to speak Latin.
Finally, let me answer your question.
In English you could add a parenthetical "I think", like this:
Latin is easy to me, I think.
In Latin, a similar remark could be worded as credo (I believe) or puto (I think).
The ut opinor suggested by Hugh is also a good option, and can be used similarly.
(Also, tibi is second person, meaning roughly "to you". Perhaps you meant mihi, but that would be weird, too.)