I don't believe all speak with tongues. And it's not something that should be forced, either. People can pray for a gift, but they shouldn't be coerced into trying to generate something themselves.
Some people assume that speaking in tongues is only for evangelism. But that doesn't have support in scripture. In I Corinthians 12-14, tongues and interpretation are among the gifts given to the body for the common good. They edify the church.
In Acts 2, God arranged to have people present who would understand the tongues He gave the disciples. But in I Corinthians 14, this was apparently not the case in church meetings where 'no man understandeth him' and an interpreter was needed. In Acts 2, we do not read that the apostles preached the Gospel in tongue. They spoke of the wonderful works of God. But people repented after they heard Peter preaching the word, apparently in some common language.
Paul was very careful how he worded I Corinthians 14 to correct the Corinthians' mistake of speaking in tongues without intepretation in church-- an activity that only edified the individuals doing it, while activities done in the assembly should edify the congregation. During his discussion of the issue we learn that.
- speaking in tongues is edifying to the speaker.
- it only edifies the congregation if it is interpreted
- the speaker's understanding is 'unfruitful' when he speaks in tongues (he doesn't understand.)
- when one prays in tongues his spirit prays
- one can give thanks well in tongues.
Paul finally gives some specific instructions regarding speaking in tongues in verses 27-28. The church may not forbid speaking in tongues, but speaking in tongues must be done according to these guidelines, which require the one speaking in tongues to be silent in the church (and speak to himself and to God) if there is no interpreter. Paul's instructions for the church, which he later explains are commandments of the Lord, allow for 'every one of you' to edify the congregation in accordance with the order he gives in the chapter. The speaker in tongues may speak according to this order, and so may the interpreter. The prophets may speak, and all may prophesy. Verse 26 shows us that individuals may share psalms or teachings as well.
Paul describes tongues as a sign to them that believe not. Like the northern tribes in the book of Isaiah who would not hear when God spoke to them of men of other tongues and other lips, so is the case of those who hear speaking in tongues. The sign 'and yet for all that, they will not hear Me' is fulfilled when people hear speaking in tongues and respond with unbelief. We see this in the example Paul gave in I Corinthians 14 of all in church speaking in tongues and the unbeliever or unlearned who come in saying 'ye are mad.' In Acts 2, we see that some responded to speaking in tongues with scoffing and accusations of drunkenness as well.